MST 13 (MST13)
Kühlungsborn,
19 - 23 March 2012
Solar
diurnal tides in the middle atmosphere: Interactions with the zonal-mean flow,
planetary waves and gravity waves
Ulrich Achatz 1, Fabian Senf 2, Norbert Grieger 3, Thomas Kessemeier 1
1 Goethe-Universität Frankfurt, Frankfurt/Main, Germany
2 Leibniz-Institut für Troposphärenforschung, Leipzig, Germany
3 Leibniz-Institut für Atmosphärenphysik, Kühlungsborn, Germany
The
dynamics of solar tides is investigated with regard to variations of the
background atmosphere, including planetary waves (PW), and to the interaction
with gravity waves (GW). (1) Using a linear model with a clear cause-effect
relationship, it is shown that planetary waves play an important role in tidal
dynamics, most importantly by inducing non-migrating tidal components from a
migrating thermal forcing. (2) Ray-tracing simulations are used to analyze the
GW force on the large-scale flow including the solar tides. In comparison to
classic GW parameterizations, the inclusion of time-dependence and horizontal
refraction leads to a significant decrease of the GW drag. (3) If time is left
nonlinear effects of tidal dynamics will be discussed as well.
Presented by: Achatz, Ulrich
Performance
improvement in momentum flux computation time using EV based post beam steering
technique derived winds
VK Anandan , Kumar Shridhar , VN Sureshbabu
ISTRAC, Indian Space Research Organisation, Bangalore, India -560058
Vertical
flux of horizontal momentum of wind fluctuations have been a key parameters for
radar measurements in the lower and middle atmosphere. Several studies have
presented on error analysis and statistical reliability of the method focusing
on various beam configurations. To obtain statistically significant
measurements of the momentum flux, long integration times are necessary as the
flux is typically a small fraction of the geometric mean energy. The estimate
of momentum flux of short-period (T <2 h) wind fluctuations together with
the uncertainties in estimation at Jicamarca and concluded that momentum flux
estimates exceeding the measurement uncertainties can be obtained after about
one day of integration. In another study momentum flux estimated for short
period (T <2h), integrated for the different length of times to minimize the
error and concluded that optimum time of integration for estimation of momentum
flux is about 15-16 hrs.
In
this paper a study has been carried out on Vertical flux of horizontal momentum
using EV based post beam steering technique in deriving winds from the
observations of middle and upper atmospheric (MU) radar at Shigaraki, Japan in
multi channel receiver mode. The vertical flux of horizontal momentum has been
calculated with four off-zenith beams in 32 different azimuth direction with a
beam tilt of 1.5 deg based on symmetric beam method with necessary modification
for accommodating different azimuth direction. By this way 8 set of zonal and
meridional momentum flux value has been obtained and mean value found. Momentum
flux is estimated on 14 hrs observation and statistics are computed. It is
observed that the mean value of zonal and meridional momentum flux is ranging
between -0.1 to 0.25 m2s-2 and -0.1 to 0.15 m2s-2
respectively for the given day of observation. The statistical study
reveals that an irreducible error in is observed by 7-8 hrs integration which
is best in the results reported earlier. The value of errors in various ranges
are in zonal momentum flux is of the order 0.0280 m2s-2 for
1.05–12 km, 0.0310 m2s-2 for 12–16 km and 0.0250 m2s-2
for 16–20 km and in meridional momentum flux is of the order 0.010 m2s-2
for 1.05–12 km, 0.030 m2s-2 for 12–16 km and 0.0120
m2s-2 for 16–20 km. The study has revealed that a
statistically reliable momentum flux observation can be obtained with in a
period of 7-8 hrs using the new approach in deriving the winds using EV based
post beam steering technique.
Presented by: Anandan, VK
Extraction
of horizontal wind velocities from a multi receiver phased array radar system using
post beam steering technique and efficiency of various beamforming methods
VK Anandan 1, VN Sureshbabu 1, Toshitaka Tsuda 2, Jun-ichi Furumoto 2
1 ISTRAC, Indian Space Research Organisation, Bangalore -58, India
2 Research Institute for Sustainable Humanosphere (RISH), Kyoto
University, Uji, JAPAN
Multi-receiver
data analysis broadly divided in space antenna (SA), imaging Doppler
interferometry (IDI) and post beam steering (PBS) techniques. DBS has proven to
be a reliable means of obtaining the wind vector, other multi receiver methods
have also been developed which have proven to have distinct advantages, such as
larger signal-to-noise-ratio (SNR) and higher angular resolution.
PBS
technique was initially demonstrated in wind profiling by Rottger and Ierkic
(1985) as a means of software steering using multi receiver data. Since these
measurements typically involve reception on minimum three spatially separated
arrays, a systematic phase shift can be applied to the signals to produce a
two-way beam pattern in any arbitrary direction within the volume illuminated
by the transmitted beam.
In
this paper a study has been carried out using spectral based technique on data
received from middle and upper atmospheric (MU) radar at Shigaraki, Japan. The
array is also capable of steering the beam electronically using phase shifters
in transmit and receive path. The experiment was conducted with full array of
transmission (beam width 3.6o) in vertical direction. The data
collected was subjected to PBS using different digital beam forming algorithms,
such as Bartlett, Capon, Multiple Signal Classification (MUSIC) and Eigen Value
(EV) based method. In all approach beam is formed at 1.5o
off-vertical and radial vectors of winds were determined in azimuth angle separated
by 5.6o. The wind profiling that ranges from 1km to 19km is carried
out using adaptive moments estimation technique. From
the radial velocity obtained, zonal and meridional velocities were computed
using least square method.
Results
obtained are compared with the wind velocity estimated using the observation
conducted in DBS method and GPS sonde observed wind velocity in near time. The
results are in good agreement shows capabilities of various beam forming
approaches in deriving the wind velocity using PBS. Performances of different
algorithms were also studied and the results will be discussed in detail. This
is the first time that various beam forming techniques have been applied
through the spectral estimation methods and derived the 3-D wind velocities
from atmospheric radar signals and also performances of the algorithms have
been reported.
Presented by: Anandan, VK
Performance
analysis of optimum tilt angle with necessary beam configuration to minimize
error in measurement of horizontal wind velocities derived by Post Beam
Steering technique
VN
Sureshbabu 1,
VK Anandan 1,
Toshitaka Tsuda 2,
Jun-ichi Furumoto 2
1 ISTRAC, Indian Space Research Organisation, Bangalore-58, India
2 Research Institute for Sustainable Humanosphere (RISH)
3-D
wind profiling of atmosphere becomes very important for meteorological purpose
and atmospheric research. Various techniques have been used and most popular is
the radar based operating at VHF and UHF frequencies popularly called as ST/MST
radar or wind profilers. Using atmospheric radars also wind velocity can be
estimated using different approaches such as Doppler beam swinging (DBS),
spaced antenna (SA) drift, and post beam steering (PBS). PBS can be mentioned
as an extension of DBS where the beam is formed in different direction from
data received from vertically transmitted beam having sufficient beam width.
Essential requirement of PBS is the formation of steering vectors with the
concept of spatial filters using weighting vectors to maximize the gain in a
steered direction and reject the undesired signals. The receive beam formed
should be within the transmit beam to have better signal-to-noise-ratio (SNR).
A
study has been carried out using spectral based technique on data received from
middle and upper atmospheric (MU) radar at Shigaraki, Japan. MU radar is a
monostatic pulsed phased array radar operates at 46.5 MHz with a peak power of
1 MW. The array is configured as circular array of 475 crossed Yagi elements
which are grouped and formed 25 different receiver channels for observational
purpose. The array is also capable of steering the beam electronically using
phase shifters in transmit and receive path. The experiment was conducted with
full array of transmission (beam width 3.6o) in vertical direction.
The data collected were subjected to PBS using different digital beam forming
algorithms, such as Bartlett, Capon, Multiple Signal Classification (MUSIC) and
weighted subspace fitting (WSF) for different tilt angle starting from 1o
to 1.9o. The beams are formed in the numbers from 4 to 64 equally
separated azimuth directions to obtain the radial wind velocity. From the
radial velocity obtained, zonal and meridional velocities were computed using
least square method.
Results
show that wind velocity estimated at tilt angle of 1.5o has given
very good agreement on wind estimated in comparison with the wind estimated
using DBS technique and GPS sonde based observation. It is also observed that
the difference is minimal when number of beams used is more than 16 for the
estimation of zonal and meridional velocities.
Presented by: Anandan, VK
An
inter-comparison of wind velocities in different observation approaches and
signal processing techniques using multi receiver phased array MU radar system
Kumar
Shridhar 1,
VN Sureshbabu 1,
VK Anandan 1,
Toshitaka Tsuda 2,
Jun-ichi Furumoto 2
1 ISTRAC, Indian Space Research Organisation, Bangalore -58, India
2 Research Institute for Sustainable Humanosphere (RISH), Kyoto
University, Uji, JAPAN
Application
of ST/MST radars for observing back ground air motion and deriving 3-D wind
velocities has been well established. Today, numerous techniques and methods
are available for deriving horizontal wind velocities. Among them Doppler beam
swinging is the most popular because of its simplicity by using a single
receiver and tilting the beam to minimum three non-coplanar direction one after
the other using phase shifters. There are multi receiver phased array radar
systems in operation for complimenting and supplementing the observations
limited by DBS based system. Multi-receiver data analysis broadly divided in
space antenna (SA), imaging Doppler interferometry (IDI) and post beam steering
(PBS) techniques. DBS has proven to be a reliable means of obtaining the wind vector,
other multi receiver methods have also been developed which have proven to have
distinct advantages, such as larger signal-to-noise-ratio (SNR) and higher
angular resolution.
In
this paper we are presenting a detailed study on wind velocities derived in
different observation method and signal processing techniques on the
observation conducted with middle and upper atmospheric (MU) radar at
Shigaraki, Japan. A modified signal detection approach has been used for
deriving the wind velocities using SA technique thereby able to detect the
signal upto 18-19km. This has been reported in a companion paper. The same data
has used under various Post Beam Steering algorithms and wind velocities were
derived. During the observation period radar also operated in DBs mode for
shorter duration to obtain DBS based wind velocities. There was an independent
observation of winds using GPS sonde observation also recorded. Analysis is
carried out on 12hrs of observation, various statistical parameters on winds
derived from different approach have been determined. Inter comparison of
results shows a very good comparison of all parameters. The result confirms the
robustness and reliability of the new algorithms in deriving 3-D winds.
Presented by: Anandan, VK
Observation
of horizontal wind velocities in presence of convective system using multi
receiver phased array MST radar system
VK Anandan 1, VN Sureshbabu 1, Rao S Vijayabhaskara 2
1 ISTRAC, Indian Space Research Organisation, Bangalore -58, India
2 Dept. of Physics, SV University, Tirupati, India
One
of the most important uses of ST/MST radars is measurement of horizontal winds.
Today, numerous techniques and methods are available for deriving 3-D
atmospheric winds using radar remote sensing. Among them Doppler beam swinging
is the most popular because of its simplicity by using a single receiver and
tilting the beam to minimum three non-coplanar direction one after the other
using phase shifters. There are multi receiver phased array radar systems in operation
for complimenting and supplementing the observations limited by DBS based
system. Once the wind fields are changing with in the beam dwell time during
convective condition prevails over the observation area, DBS technique fails in
deriving the horizontal wind velocities. So there is not much observations were
reported on observation of horizontal velocities during convective condition
using ST/MST radars.
A
study has been conducted on observation of horizontal wind velocities during
convective condition with middle and upper atmospheric (MU) radar at Shigaraki,
Japan using EV based post beam steering (PBS) techniques. The advantage of this
approach is that all the wind fields are derived for the given instant of time,
so the derived winds in all direction will be reliable and accurate. In EV
based PBS technique, beam is formed at 1.5o off-vertical and radial
vectors of winds were determined in azimuth angle separated by 5.6o.
This technique has been validated in observation with clear air condition and found
to be most reliable and accurate in all post beam steering techniques. Data
analysis is carried out on a few number of occasions were convective system was
prevailing in the atmosphere. 3-D wind velocities were derived in all cases
with very high temporal resolution. The spatial (over the range) and temporal
observation helps in identifying the kinematics convective system and the same
will be presented in workshop.
Presented by: Anandan, VK
Improved
performance in Horizontal wind estimation from a multi receiver phased array
atmospheric radar system using Spaced Antenna Drift Technique and signal
processing approaches
Kumar
Shridhar 1,
VK Anandan 1,
Toshitaka Tsuda 2,
Jun-ichi Furumoto 2
1 ISTRAC, Indian Space Research Organisation, Bangalore -58, India
2 Research Institute for Sustainable Humanosphere, Kyoto University,
Uji, JAPAN
The
Spaced Antenna (SA) drift method is multi receiver alternatives to Doppler beam
swinging (DBS) and has been studied thoroughly in the literature. Like the DBS
technique, a standard SA experiment uses a single array for transmission but
receives the returned signals on three spatially separated antennas with
non-collinear baselines. A baseline is defined as the imaginary line drawn
between the receiving centers. Assume that the three receivers exist at the
vertices of a right angle triangle with the sides along the x and y axes. By
calculating the cross-correlation functions between the signals received at the
different receivers, one can obtain the delay times along x and y axes. By
knowing these delays and receiver separation, horizontal velocities can be
estimated.
Middle
and upper atmospheric (MU) radar at Shigaraki, Japan is an excellent system to
carry out observation using spaced antenna techniques. The array is configured
as circular array of 475 crossed Yagi elements which are grouped and formed by
25 different receiver channels for observational purpose. Numerous scientific
studies were reported in the past. In most of the studies the array is divided
in to three segments and grouped with 3/6 channels to form equilateral triangle
base line. In all this studies the wind is estimated up to a maximum height of
10 -14 kms. In general SA based wind estimation could not give good height
coverage due to smaller aperture being used for received signals. This will
result in poor signal-to-noise-ratio (SNR) and cross correlation between
different antenna groups will be low. In this study we have made use of complete
array for transmission and received the signal with 25 receiver channels. The
receiver channels are divided in to three equal segments and form the baseline
suitable to derive the wind velocity using spaced antenna technique. Complete
analysis is repeated with 4 different spatial distributions of array group. In
each case wind velocity is estimated and quality check is carried out.
Velocities from all groups were averaged to obtain the final value. The
identification of receive channels for grouping and its phase centers were
critical to get the best result in cross correlation and determining the
velocity. The results were compared with the wind velocity estimated using DBS
technique and wind observed by the GPS sonde. It is observed that the new
approach adopted using spatially distributed array grouping has yielded higher
height coverage upto 18 to 20 kms and in good agreement with the results
obtained using DBS and GPS sonde observations.
Presented by: Anandan, VK
ESRAD
Radar observations of PMSE during the PHOCUS rocket campaign at ESRANGE on 21
July 2011 07 UTC: preliminary results of coherent radar imaging.
Joel Arnault , Sheila Kirkwood
Polar Atmospheric Research, Swedish Institute of Space Physics, Kiruna, Sweden
The
summer polar mesosphere has the particularity to provide favorable conditions
for ice-crystal cloud formation, particularly at mesopause heights around 80
km. These are known as noctilucent clouds that can eventually be seen from
midlatitude regions at dawn / dusk time when the sun illuminates only the upper
atmosphere. However noctilucent clouds cannot be seen from polar
regions where they can only be detected remotely with lidar
measurements. The aim of the PHOCUS campaign that was held in
ESRANGE, North Sweden, in June-July 2011, was to launch a rocket up to the
mesopause in order to provide in-situ and collocated measurements of such
clouds.
Lidar observations of noctilucent clouds are generally associated with enhanced
VHF radar echoes, known as polar mesosphere summer echoes (PMSEs). However
PMSEs and noctilucent clouds are not exactly collocated since the strength of
PMSEs depends on more factors than only the particles' size that eventually
make the noctilucent clouds visible (fluctuations in the refractive index at
the Bragg scale, the refractive index depending on temperature, water vapor,
and also electron density).
When the rocket of PHOCUS campaign was launched on 21 July 2011 07 UTC a strong
PMSE was detected by the VHF ESRAD radar at ESRANGE. Since ESRAD radar has six
receivers, interferometric imaging techniques can be used to represent the
radar signal back-scatterers in 3D. In particular coherent radar imaging allows
discriminating different scatterers according to their height, their angular
position within the probed volume and their radial velocity, which eventually
help improving our understanding of the physics of PMSEs. A preliminary
investigation of such coherent radar imaging results will be presented here.
Presented by: Arnault, Joel
Dynamical
influence of a gravity wave generated by the Vestfjella Mountains in
Antarctica: radar observations, fine-scale modeling and kinetic energy budget
analysis
Joel Arnault , Sheila Kirkwood
Polar Atmospheric Research, Swedish Institute of Space Physics, Kiruna, Sweden
A
remarkable case-study of mountain wave generated by the Vestfjella Mountains
(in western Droning Maud Land, Antarctica, southwest of the Finnish / Swedish
Aboa / Wasa station) has been observed with the Moveable atmospheric radar for
Antarctica (MARA) during the SWEDish Antarctic Research Programme (SWEDARP)
from 9 to 13 December 2007. The radar observations are compared with a Weather
Research Forecast (WRF) model experiment operated at 2 km horizontal
resolution. The role played by this particular gravity wave on the atmospheric
flow is then quantified with a kinetic energy budget analysis computed in the
simulation (tendency of horizontal kinetic energy = horizontal advection +
vertical advection + horizontal
work of pressure forces + frictional dissipation). The results show that this particular
mountain wave reached lower-stratospheric heights, where it broke through
convective overturning and generated an inertia gravity wave with a smaller
vertical wavelength, in association with a depletion of kinetic energy through
frictional dissipation and negative vertical advection. The kinetic energy
budget also shows that this gravity wave accelerated locally the horizontal
flow
through positive vertical advection, suggesting a process more complicated than
what is usually proposed. Moreover the apparently strong influence that this
gravity wave had on the other terms of the budget, i.e horizontal advection and
horizontal work of pressure forces, suggests that evaluating the influence of
gravity waves on the mean-flow with the vertical advection term alone is not
sufficient.
Presented by: Arnault, Joel
Estimation
of absolute meteor fluxes from specular meteor observations
Carsten Baumann , Gunter Stober , Ralph Latteck ,
Werner Singer
Institute of Atmospheric Physics Kühlungsborn
Until
today the total meteoric mass input into the mesosphere-lower-thermosphere
(MLT) region is still a matter of intense research. Currently available
estimates vary over a large range from 10 to 200 tons per day underlining the
inherent uncertainties of these values.
A
small part of this extraterrestrial meteoric debris is observed by specular
meteor radars. Here we present a method which derives absolute meteor fluxes
from meteor count rate observations for the sporadic meteor sources and the
Geminid meteor shower. The particle size and velocity distribution is
determined using a single body meteor ablation model and measurements of the
electron line density, which is directly related to the meteoroid mass.
Finally, the estimated meteor fluxes for a mean detectable meteoroid size are
compared to the meteor fluxes given by Ceplecha, 1998.
Presented by: Baumann, Carsten
Main
characteristics of polar mesosphere summer echoes observed with the MST radar
ESRAD, Kiruna, Sweden during 1997- 2011
Evgenia
Belova 1, Maria Smirnova, Sheila Kirkwood 1
1 Swedish Institute of Space Physics
Since
1997 measurements of polar mesosphere summer echoes (PMSE) have been carried
out with the 52 MHz ESRAD MST radar located near Kiruna in Northern Sweden.
Importantly, these measurements have been made using the same height resolution
and pulse-modulation scheme the whole time . ESRAD has
been calibrated against radiosondes that allow us to calculate PMSE
cross-sections corrected for changes in transmitter output and antenna feed
losses from year to year. We analysed the short- and long-term variations as
well as trends in the PMSE occurrence and volume reflectivity together with the
factors affecting them. We also estimated the in-beam PMSE aspect sensitivities
using the FCA technique.
Presented by: Belova, Evgenia
Rain
kinetic energy measurement with a UHF wind profiler: application to soil
erosion survey of a tropical volcanic island
Bernard
Campistron
1, Anne Réchou 2
1 Observatoire Midi Pyrénées, Toulouse University
2 Laboratoire de l'Atmosphère et des
CYclones, La Réunion University
Land
degradation by rainfall events is strongly dependent of the kinetic energy of
raindrops that impact the soil. The approach presented here for the assessment
of soil erosion is done with UHF wind profiler observations
that in spite of a relative long wavelength is very sensitive to the
detection of rain even weak such as drizzle. For this frequency band, radar
data analysis is facilitated by the fact that attenuation by hydrometeors is
negligible and that rain backscattering belongs to the Rayleigh approximation.
Drop vertical kinetic energy flux related to the drops terminal fallspeed
combined with air vertical velocity, and drop horizontal kinetic energy flux due to drop entrainment by horizontal wind are ones of
the most pertinent parameters of rainfall erosivity. We derive in this study
the retrieval equations of these two quantities along with those of the
precipitation rate function of the mean reflectivity, vertical velocity and
horizontal wind provided by the profiler. The analysis is based on the main
assumptions of gamma raindrop size distribution and on negligible air vertical
velocity. Tests based on the values of reflectivity, vertical velocity,
spectral width and skewness of the Doppler spectra are used to discard data
that do not fulfill the requirements such as echoes from clear air or snow or
from atmospheric regions associated with substantial air vertical motion. The
calibration of the profiler using ground raingauge data is also presented. The
last part of the work shows an application of the methodology to rain
observations collected by a UHF wind profiler located at La Reunion island in the Indian Ocean. This mountainous island, that culminates at an altitude of 3000 m, has a
regime of tropical precipitation enhanced by orography. In that case the radar
provided continuous measurement of rain rate and rainfall kinetic energy from
600 m above ground level up to the summit of the island.
Presented by: Campistron, Bernard
Water
vapor analyses in mixed-phase clouds
Edwin
Campos
Mixed-phase
clouds (clouds that contain interacting liquid and ice particles) play a
significant role on the energy budget at the earth surface through modulation
of radiative fluxes in cold regions. Mixed-phase clouds are also a frequent
atmospheric hazard, particularly when its supercooled droplets are abundant
enough to disturb aviation and ground transportation.
For
monitoring water-phase dynamics in mixed-phase clouds, this work analyzes
vertical profiles of air vapor pressure, and equilibrium vapor pressure over
liquid water and ice. Based only on the magnitude ranking of these vapor
pressures, we identified conditions where liquid droplets and ice particles
grow or deplete simultaneously, as well as the conditions where droplets evaporate
and ice particles grow by vapor diffusion. The method is applied to snowstorm
observations by microwave profiling radiometer and 915 MHz wind profiler radar.
The
results corroborate well with independent radiometer retrievals of
vertically-integrated liquid water, reflectivity factor and Doppler velocity
observations by vertically-pointing radars, and radiometer estimates of
liquid-water layers aloft. This translates in a positive contribution toward
monitoring and nowcasting the evolution of supercooled droplets in winter
clouds.
Presented by: Campos, Edwin
Aspects
of Hydrometeor Scattering for Applications in the New Generation of Weather
Radars
Madhu
Chandra
Technische Universität Chemnitz
In
general, hydrometeor scattering properties play a fundamental role in the
application and design of weathers radars. Weathers radars, in the recent
years, have witnessed several advances in the areas of: polarisation diversity,
high frequency applications (above C-Band), and interpretation of diverse
polarimetric phases. Central to all these innovations are the polarisation and
frequency dependent scattering properties of hydrometers. In this contribution,
the relevant scattering behaviour will be examined with the help of both actual
radar measurements and model based scattering calculations. The polarisation
and frequency based features crucial to the interpretation of radar echoes will
be highlighted in the context of application. As a by-product, we shall also
address the scattering behaviour expected at rather high frequencies of 24 and
77 GHz. Such high frequencies are now not out-of-question because of the
emerging compact weather radar applications.
Presented by: Chandra, Madhu
Aperture
synthesis radar imaging in coherent scatter radars: Results and lessons from
Jicamarca
Jorge Chau 1, D.L. Hysell 2, M. Urco 1
1 Radio Observatorio Jicamarca, Instituto Geofísico del Perú, Lima
2 Earth and Atmospheric Sciences, Cornell University, Itahca, NY,
USA
Aperture
synthesis imaging offers a means of observing atmospheric phenomena in three
spatial dimensions with fixed-beam coherent scatter radars. The data supporting
the imagery are cross-spectral visibility estimates obtained from spaced
receivers on the ground. Extracting imagery from the data is an inverse problem
and prompts an investigation of the existence, uniqueness, and stability of the
solution. We describe different approaches to the imaging problem including
nonparametric and parametric methods, with special emphasis on the MaxEnt
algorithm, a Bayesian inversion scheme that uses Shannon's entropy as a prior
probability estimate. Finally, we present results and lessons from experiments
to observe ionospheric plasma density irregularities using coherent scatter
data from the Jicamarca Radio Observatory.
Presented by: Chau, Jorge
Aspect
sensitivity of clear-air measured by coherent radar imaging
Jenn-Shyong
Chen 1, Jun-ichi Furumoto 2
1 Department of Computer and Communication Engineering, Chienkuo
Technology University, Taiwan
2 Research Institute for Sustainable Humanosphere, Kyoto University,
Japan
Aspect
sensitivity of refractivity irregularities in the clear-air was examined with
multiple-receiver coherent radar imaging (CRI) of the MU VHF atmospheric radar
in Japan. The so-called aspect angle, which is a measurement of aspect
sensitivity, was estimated. Two CRI parameters retrieved by the Capon method
were utilized to estimate the aspect angle: brightness width from vertical
radar beam, and direction of arrival (DOA) of echo center from oblique radar
beam. Differing from previous studies with CRI, however, a mitigation of radar
beam weighting effect on the CRI brightness distribution was made before
estimating the two CRI parameters.
To
mitigate the radar beam weighting effect, the intensity distribution of the
radar beam was described with a Gaussian function, and moreover, the standard
deviation of the Gaussian function, defined as the radar beam width, was
recommended to be adaptive to signal-to-noise ratio (SNR) of data as well as
off-beam direction angle. Such kind of adaptable beam width has been proposed
in our previous study to be able to yield a more reliable CRI brightness.
Observations
showed that the aspect angles obtained from the modified brightness width of
vertical beam were larger than those of without modification, and they were
very close to the values derived from the DOA of 1o-oblique radar
beam, suggesting consistent results of the two approaches around the zenith.
Moreover, the aspect angle derived from DOA varied with radar beam direction,
which is similar to that suggested by some other methods such as comparison of
echo powers of two different oblique radar beams. However, the DOA-approach
yielded a larger aspect angle in the lower-SNR condition, as compared with the
method of comparison of echo powers. Such characteristic of aspect angle gives
a benefit: altitudinal variation of aspect sensitivity is more explicit and so
the layers with high aspect sensitivity can be identified more clearly. This
study has shown an application of adaptable radar beam width, and recommended a
feasibility of improving the measurements of atmospheric parameters with CRI
after removing the radar beam weighting effect from the CRI brightness.
Presented by: Chen, Jenn-Shyong
Introduction
to the Kunming atmospheric radar facility (KARF) and the initial results
Jinsong
Chen 1, Lei Zhao 1, Na Li 1, Jian Wu 1, Jiyao Xu 2
1 China Research Institute of Radiowave Propagation
2 Center for Space Sciences and Applied Research, Chinese Academy of
Sciences
In
the late 2000s China Research Institute of Radiowave Propagation (CRIRP) has
further expanded its research program to monitor the Earth's middle and upper
atmosphere. In attempt to study the dynamics of the MLT region in lower
latitude over China, the Kunming atmosphere radar facility (KARF) consisting of
a MF radar, an all-sky meteor radar and a ST Doppler radar with meteor radar
capability was installed at Kunming Radio Observatory (25.6o N, 103.8o E), 130
km northeast of Kunming which is the capital city of Yunnan Province, in August
2008 by CRIRP. Since then, continuous observation of winds in the MLT has been
underway. KARF gives us opportunity to complement the study of atmosphere
oscillations in low-latitude MLT region and the nonlinear interaction between
atmospheric waves and ionosphere.
The
initial results from the KARF during the first observation will be given, which
include seasonal variations of tides and gravity waves from MF radar as well as
the electron density in D region from Aug. 2008 to Jul. 2009. Also some
outcomes from two special experiments launched on the KARF will be presented in
this lecture. One involves meteors studied with the ST radar, and the other is
related to winds observed simultaneously by the MF radar and two meteor radars
with different frequencies in the Kunming site.
Presented by: Chen, Jinsong
An
Investigation of Clear-air Scatter at Radio and Acoustic Frequencies
Phillip
Chilson 1, Charlotte Wainwright 1, Christopher Wilson 1, Timothy Bonin 1, Phillip Stepanian 1, Daniel Russell 1, Abraham Frei-Pearson 1, Robert Palmer 1, Evgeni Fedorovich 1, Danny Scipion 2
1 University of Oklahoma, School of Meteorology
2 École polytechnique fédérale de Lausanne
Active
remote sensors such as radar wind profilers (RWP) and monostatic sodars rely on
gradients in fields of refractive index and temperature, respectively, to
generate backscattered signals from the atmosphere that can be monitored and
interpreted. For the case when these gradients are generated by homogeneous and
isotropic turbulence in the inertial subrange, the intensity of the
backscattered signal can be related to the relevant structure function
parameters: Cn2 for RWPs and CT2
for sodars. We have been developing a multi-platform and multi-sensor approach
based on empirical and simulated results to investigate the role of clear-air
turbulence (CAT) on radar and sodar signal strengths collected in the stable
and convective atmospheric boundary layer (ABL). Instrumentation incorporated
into the study includes a sodar; a UHF RWP; small, instrumented unmanned aerial
vehicles (UAV); instrumented meteorological towers; and rawindsondes. A
large-eddy simulation (LES) code is used to generate dynamic and thermodynamic fields representative of the stable and convective ABL under
realistic conditions. We have also developed virtual instruments capable of
ingesting output fields from the LES and emulating the types of data produced
by the RWP, sodar, and UAVs used in the study. Using the LES outputs we are
able to determine the structure functions for temperature and the refractive
index and, when applicable, the corresponding structure function parameters.
Additionally, we have developed a means of estimating the structure function
using data from the instrumented UAV and virtual UAV. In this presentation we
i) briefly discuss the virtual sodar, RWP, and UAV; ii) describe the method of
retrieving structure function parameters from our UAV observations; iii)
compare results from the various platforms and methods; and iv) consider the
applicability of different scattering theories for the atmospheric conditions
being considered.
Presented by: Chilson, Phillip
Radar
Atmospheric Imaging Techniques: An Overview
Phillip
Chilson
University of Oklahoma, School of Meteorology
On
the most fundamental level, an atmospheric radar’s
spatial resolution is prescribed by the aperture of its antenna and duration of
the transmitted pulse (and corresponding filters). The recipe to enhance
resolution is simple: increase the effective area of the antenna to achieve
better angular resolution and transmit / receive narrower pulses to improve
range resolution. However, it may not always be feasible to implement these
modifications on account of such factors as construction cost or space
limitations or frequency limitations. Moreover, radars with narrow beam widths
can only detect a limited region of the atmosphere at a given time. Therefore
the beam must be mechanically or electronically scanned in order to observe a
larger swath of the atmosphere. Ideally, one would like to produce a wide-angle
“snapshot” of the atmosphere while still maintaining good angular and range
resolution. This can be achieved using imaging techniques. This presentation
provides an introduction to radar atmospheric imaging techniques and
illuminates some of the benefits and pitfalls associated with them. Several
examples of radar systems that utilize imaging techniques along with
observations collected with them are presented and discussed.
Presented by: Chilson, Phillip
Implementation,
Calibration, and Testing of Range Imaging on the Lindenberg 482-MHz Radar Wind
Profiler
Phillip
Chilson 1, Volker Lehmann 2
1 University of Oklahoma, School of Meteorology
2 Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg
In
November 2009, a new 482-MHz Radar Wind Profiler (RWP) was installed at the
Meteorological Observatory Lindenberg (MOL) in Germany. The shortest pulse used
by the system is 1.0 µs (corresponding to a nominal range resolution of 150 m)
and the occupied bandwidth is about 1.7 MHz. The system is equipped with a
digital receiver RVP-910 and it is possible to operate the RWP in a range
imaging (RIM) mode using five different carrier frequencies within the
bandwidth of the system. Two sets of experiments have been conducted in 2010
and 2011 to i) test the RIM functionality on the 482-MHz RWP, ii) explore
possible frequency sets for operational use, iii) develop a means of
calibrating the RWP for RIM operation, iv) operate the RWP in RIM mode during
several meteorlogical events, v) develop RIM analysis software for the RWP, and
vi) compare the RIM results with other data sets. In this presentation we
provide an overview of the RIM capabilities of the Lindenberg 482-MHz RWP along
with first results from these experiments.
Presented by: Chilson, Phillip
The
Wave-Driven Circulation and Variability of the Wintertime Arctic Middle
Atmosphere
Richard
Collins 1, Amal Chandran 1, V. Lynn Harvey 2, Kohei Mizutani 3, Michael Gerding 4, Gerd Baumgarten 4, Anja Stromme 5, Rolando Garcia 6, Daniel Marsh 6
1 University of Alaska Fairbanks
2 University of Colorado Boulder
3 National Institute of Information and Communications Technology
4 Leibniz Institute of Atmospheric Physics
5 SRI International
6 National Center for Atmospheric Research
An
international network of four Rayleigh lidars located in observatories at
Andoya, Norway (69°N, 16°E), Chatanika, Alaska (65°N, 147°W), Kangarlussuaq,
Greenland (67°N, 51°W) and Kühlungsborn, Germany (54°N, 12°E) provide a chain
of measurements from the eastern Arctic to the western Arctic under distinct
synoptic regimes (i.e., the Arctic stratospheric vortex, the Aleutian
anticyclone, the stratospheric surf-zone). In this paper we present the use of
satellite measurements, lidar measurements, meteorological analyses, and model
simulations to understand the wave-driven circulation and variability of the
polar atmosphere. Recent Arctic winters have seen major disturbances in the
wintertime circulation associated with major Sudden Stratospheric Warming and
Elevated Stratopause events. These disturbances are associated with major
changes in the planetary wave and gravity wave forcing of the circulation. The
lidars yield high-resolution temperature and density measurements that allow
characterization of the planetary waves, tides, and gravity waves. The
satellite observations yield synoptic-scale temperature measurements of the
mesosphere and upper stratosphere while the meteorological soundings and
analyses provide synoptic-scale measurements of the troposphere and lower
stratosphere. The Whole Atmosphere Community Climate Model provides both
free-running and specified dynamic simulations that allow investigation of the
observed planetary and gravity wave activity in the Arctic atmosphere. We use
this approach to study the circulation at local, regional and global scales. We
present results from recent International Polar Year observations, analysis,
and simulations associated and discuss current and future studies.
Presented by: Collins, Richard
Resonance
lidar measurements of atomic energy states in the auroral E-Region
Richard
Collins 1, Xinzhao Chu 2, Zhibin Yu 2, Chester Gardner 3, Michael Nicolls 4
1 University of Alaska Fairbanks
2 University of Colorado Boulder
3 University of Illinois at Urbana-Champaign
4 SRI International
Resonance
lidar observations at Chatanika, Alaska have revealed the presence of large
high-altitude sodium layers (~ 110 km) during active aurora [Collins et al.,
1996]. More recently lidar observations from McMurdo, Antarctica have revealed
the presence of atomic iron present in the E-Region (up to 150 km) coincident
with strong auroral displays [Chu et al., 2011]. The lidar measurements, made
with an iron Boltzmann lidar, recorded the concentration of iron atoms both in
the ground state and first excited state using the 371.993 nm and 373.713 nm
transitions respectively [Gardner et al., 2001; Chu et al., 2002]. A Boltzmann
thermal analysis of the ratio of the population of iron atoms in the excited
state to the ground state suggests temperatures that are several hundred Kelvin
higher than the expected from MSIS [Chu et al., 2011]. This
initial analysis reveals a temperature profile that has a shape and peak
amplitude that is similar to that expected for the Joule heating profiles and
provide direct observation of the thermal response of the E-region to
auroral forcing. These Antarctic lidar measurements revealed the energetics of
the neutral iron atoms, but could not document the structure of iron ions. An
Incoherent Scatter Radar (ISR) would provide plasma measurements, independent
Joule Heating estimates. In this paper we present an experiment where we use an
iron Doppler lidar [Lautenbach and Höffner, 2004; Chu et al., 2008] and an iron
density lidar [Hou, 2002] to simultaneously measure the energetics of atomic
iron in the ground and first excited state. The iron Doppler lidar provides the
population and temperature of the iron atoms using the Doppler broadening of
the 371.993 nm transition. The iron density lidar provides the population of
the iron atoms in the first excited state using the 373.713 nm transition.
Coordinated observations that combine imager, lidar, and radar observations
offer the opportunity to more fully understand the energetics of the E-region
during auroral substorms and advance our understanding of ion-neutral coupling
in the atmosphere.
Presented by: Collins, Richard
A
VHF profiler network study: Upper level divergence and the SW Ontario tornadoes
of Aug 2011.
Matthew
Corkum 1, Peter Taylor 1, ZhengQi Wang 2, Shama Sharma 1
1 CRESS, York University
2 ESSE, York University
Researchers
from York University, University of Western Ontario, and McGill University have
now completed the acquisition and installation of a Canadian regional scale
network of ten Mardoc WindTtracker VHF wind profilers (the O-QNet) in Ontario
and southern Quebec. These are providing a valuable data set of hourly and
three-hourly winds from about 400m to 15 km above the surface.
We
have made a series of comparisons with NWP model analyses and forecasts. We are
also using sets of three profilers in triangular arrays to compute upper level
divergence and vorticity as indicators of severe summer weather. The approach
was originally tested by Zamora et al (1987) but it does not appear to have been
used extensively on an operational basis. The goal is to compute divergence and
vorticity in real time and supply them to weather forecasters as an additional
tool to help identify regions with the potential for severe summer storm
development. Radiometers are also being used (by Environment Canada) to obtain
temperature and humidity profiles at one location in the region.
We
are currently looking at data for Aug 21 24, 2011 when several tornadoes
occurred in southern Ontario, including an F3 at Goderich. The profiler data
show an upper level divergence pattern crossing the region. We are also
computing divergence and vorticity patterns from the forecast models in order
to compare with the observed patterns.
Winter
cases will also be investigated to see if probable snowsquall regions can be
identified.
Zamora,
R.J., M.A. Shapiro, and C.A. Doswell, III, 1987: The Diagnosis of Upper
Tropospheric Divergence and Ageostrophic Wind Using profiler Wind Observations,
Mon. Wea. Rev., 115, 871-874.
Presented by: Corkum, Matthew
Further
investigation on stratospheric air intrusion in to the troposphere during the
episode of tropical cyclone: Numerical simulation and MST radar observations
Siddarth
Shankar Das ,
S Sijikumar , Kizhathur Narasimhan Uma
Space Physics Laboratory, Vikram sarabhai Space Centre
Stratosphere-troposphere
exchange (STE) process has been a topic of research for past several decades
due to its impact on global climate change. In this aspect, many ground based,
in-situ, satellite measurements, and modelling have been carried out to improve
our understanding of physical, chemical and dynamical processes that couples
stratosphere and troposphere. Tropical cyclone and convection are the two
source mechanisms that give raises to STE processes over tropical region.
Owning the important of STE associated with cyclone over the tropical
atmosphere, for the first time, spatiotemporal structure of stratospheric air
intrusion into the troposphere during the passage of tropical cycloneis
simulated using Advanced Research- Weather Research and Forecast (WRF-ARW)
model. The WRF-ARW simulation effectively reproduces the spatiotemporal
evolution of vertical velocity associated with tropical cyclone and shows good
agreement with the mesosphere-stratosphere-troposphere (MST) radar observations
at Gadanki (13.5oN, 79.2oE). The observed intrusion in
the upper-troposphere has a narrow band with the width of about 50 km and
stretch over 200-250 km and vertical structure of 5-6 km. This study shows that
the intrusion occurs in the periphery of the cyclone. The detail results will
be presented and discussed in the upcoming workshop.
Presented by: Das, Siddarth
Shankar
Seasonal
characteristics of Kelvin-waves in the mesosphere and lower thermosphere (MLT)
region over an equatorial station Thumba using SKiYMET meteor wind radar
Siddarth
Shankar Das
1, S Suheela 2, Anu Krishna 2
1 Space Physics Laboratory, Vikram sarabhai Space Centre
2 Dept. of Physics, University of Kerala
The
detailed study of mesosphere lower thermosphere and ionosphere region has
historically been difficult because of its relative inaccessibility to direct
measurement techniques and the complex and highly coupled processes which occur
there. However with the use of various in-situ and ground based probing
techniques of the middle atmosphere which includes MST radar, all-sky SKiYMET
meteor wind radar, the various atmospheric parameters like wind and temperature
can be measured. Tides, planetary wave and gravity wave, forced their in-situ
or at lower levels, all participates in and frequently dominates the dynamics
of this region. Lower boundaries for the thermosphere models and the upper
boundaries for the mesospheric models have been usually specified in lower
thermosphere near 80-120 km. this can be a difficult region for the
specification of the boundary condition on chemicals and energy balance models
because constituents and heat transfer occur readily between thermosphere and
mesosphere. Thus for the climate variability and weather prediction, the
thorough knowledge of the atmospheric waves especially at mesosphere and lower
thermosphere (MLT) region is required. MLT region is dynamically controlled by
the wave activities namely; gravity waves, planetary waves and tides which are
mainly originate at the lover atmosphere and dissipate their energy and
momentum fluxes in the mesospheric region. The major emphasis of the present
work was to establish the seasonal characteristics of Kelvin wave in the
mesosphere and lower thermosphere (MLT) over and equatorial station Thumba
using Meteor wind radar. The detail results will be presented and discussed in
the upcoming workshop.
Presented by: Das, Siddarth
Shankar
The
climatology, propagation and excitation of ultra-fast Kelvin waves
Robin
Davis 1, Saburo Miyahara 2, Ying-Wen Chen 2, Nicholas Mitchell 1
1 University of Bath
2 Kyushu University
Wind
measurements from a meteor radar on Ascension Island (8◦S, 14◦W)
and simultaneous temperature measurements from the Aura MLS instrument are used
to characterise ultra-fast Kelvin waves (UFKW) of zonal wavenumber 1 (E1) in
the mesosphere and lower thermosphere (MLT) in the years 2005–2010. These
observations are compared with some predictions of the Kyushu-general circulation
model. Good agreement is found between observations of the UFKW in the winds
and temperatures, and also with the properties of the waves in the Kyushu-GCM.
UFKW are found at periods between 2.5–4.5 days with amplitudes of up to 40 m/s
in the zonal winds and 6K in the temperatures. The average vertical wavelength
is found to be 44km. Amplitudes vary with latitude in a Gaussian manner with
the profiles centred over the equator. Dissipation of the waves results in
monthly-mean eastward accelera- tions of 0.2–0.9 m/s/day at heights around 95
km, with 5-day mean peak values of 4 m/s/day. Largest wave amplitudes and
variances are observed over Indonesia and central Africa and may be a result of
very strong moist convective heating over those regions. Rainfall data from
TRMM are used as a proxy for latent-heat release in an investigation of the
excitation of these waves. No strong correlation is found between the
occurrence of large-amplitude mesospheric UFKW events and either the magnitude
of the equatorial rainfall or the amplitudes of E1 signatures in the rainfall
time series, indicating that either other sources or the propagation
environment are more important in determining the amplitude of UFKW in the MLT.
A strong semiannual variation in wave amplitudes is observed. Intraseasonal
oscillations (ISOs) with periods 25–60 days are evident in the zonal background
winds, zonal-mean temperature, UFKW amplitudes, UFKW accelerations and the
rainfall rate. This suggests that UFKW play a role in carrying the signature of
tropospheric ISOs to the MLT region.
Presented by: Davis, Robin
Winds,
tides and waves in the mesosphere and lower thermosphere over Bear Lake
Observatory (42N 111W)
Kerry Day 1, Michael Taylor 2, Victoria Howells 1, Nicholas Mitchell 1
1 The University of Bath
2 Utah State University
Atmospheric
temperatures and winds in the mesosphere and lower thermosphere have been
measured simultaneously using the Aura satellite and a meteor
radar at Bear Lake Observatory (42N, 111W). The data presented in this study is
from the interval March 2008 to July 2011.
The
mean winds observed in the summer-time over Bear Lake Observatory show the
meridional winds to be equatorward at all heights during April-August and to
reach monthly-mean speeds of – 12 m/s. The mean winds are closely related to
temperatures in this region of the atmosphere and in the summer the coldest
mesospheric temperatures occur about two weeks after the strongest equatorward
meridional winds. In other seasons the meridional winds are poleward, reaching
monthly-mean values of up to 12 m/s. The zonal winds are eastward through most
of the year and in the summer strong eastward zonal wind shears of up to 4.5
m/s/km are present. However, westward winds are observed at the upper heights
in winter and sometimes during the equinoxes. Comparisons of the observed winds
with URAP and HWM-07 reveal some significant differences.
Observations
of the 12- and 24-hour tides reveal that both tides can reach large amplitudes
over Bear Lake, with monthly-mean amplitudes reaching up to 50 and 35 m/s,
respectively. Both tides display a clear seasonal cycle. The 12-hr tide
maximises in September and December-February. The 24-hour tide maximises in
March-April. Comparisons with the Global Scale Wave Model 2009 suggest that the
model effectively predicts the September maximum of the 12-hour tide, albeit at
smaller amplitudes than observed, but does not predict the winter maximum. In
the case of the 24-hour tide, the observed amplitudes are reproduced well, but
a predicted autumnal maximum is not observed.
Signatures
of the 16- and 5-day planetary waves are clearly evident. Short-lived wave
events can reach large amplitudes of up to ~ 15 m/s and 8 K and 20 m/s and 10 K
for the 16- and 5-day wave, respectively. A clear seasonal and short-term
variability are observed in the 16- and 5-day planetary wave amplitudes. The
16-day wave reaches largest amplitude in winter and is also present in summer,
but with smaller amplitudes. The 5-day wave reaches largest amplitude in winter
and in late summer. An inter-annual variability of the amplitude of the
planetary waves are evident in the four years of
observations.
Presented by: Day, Kerry
A
Mini VHF BLR and the known FCA Wind Magnitude Underestimation
Bronwyn
Dolman 1, Iain Reid 2, Andrew MacKinnon 3
1 ATRAD Pty Ltd
2 University of Adelaide & ATRAD Pty Ltd
3 University of Adelaide
Radars
utilising the Spaced Antenna (SA) Full Correlation Analysis (FCA) technique are
known to measure excellent agreement in direction, but typically underestimate
the wind magnitude, when compared to other measurement techniques. This
magnitude underestimation occurs in all regions of the atmosphere, and results
from any effect that suppresses the correct value of the cross-correlation
functions of the fading time series calculated between the antenna pairs.
ATRAD
developed a miniature Boundary Layer (mini-BL) profiler in 2003, operating at
VHF, and consisting of just 3 antennas. The system was deployed at Buckland
Park, the University of Adelaide field site, and was used in a 4 day trial,
where mini-BL wind estimates were compared to a larger 27 antenna BL profiler.
Results of the trial suggest the mini-BL measured wind magnitudes 5-10% greater
than the BL, with excellent agreement in direction. Due to equipment
requirements, these results were not investigated further.
In
2010 the mini-BL was re-installed at Buckland Park. A study was conducted in
2010, where the mini-BL was set to receive only, and listened to the transmit signal
from a nearby 55 MHz 27 antenna BL array. In late 2011 the mini-BL and BL were
run as stand-alone systems in an interleaved manner. Results from both studies
will be discussed, with particular attention to the bias discussion.
Presented by: Dolman, Bronwyn
Small
Modular 449 MHz Wind Profiling Radar – First Results
Bronwyn
Dolman 1, Iain Reid 2, Robert Vincent 3, Andrew MacKinnon 3, Richard Mayo 1, Gary Jonas 1, Jonathan Woithe 1
1 ATRAD Pty Ltd
2 University of Adelaide & ATRAD Pty Ltd
3 University of Adelaide
ATRAD
Pty Ltd has recently developed a low cost, portable,
wind profiling radar. The profiler operates at 449 MHz, using 3 Yagi antennas,
and has been designed to be capable of rapid field deployment. The system is also
modular in nature, and can be deployed as a single unit, or as an array. The
profiler uses the Spaced Antenna Full Correlation Analysis technique to measure
the vertical and horizontal wind fields from near ground to around 300 m.
First results from the deployment of
the radar will be presented.
Presented by: Dolman, Bronwyn
Single-
Compared to Dual-Frequency DSD Retrievals During
TWP-ICE
Bronwyn
Dolman 1, Christopher Williams 2
1 ATRAD Pty Ltd
2 CIRES/NOAA
Well
established techniques exist for retrieving the raindrop size distribution
(DSD) using either VHF or UHF wind profiling radars. VHF profilers are useful
tools in rainfall studies, as they receive echo from both clear-air and
precipitation with roughly equal magnitude. A major limitation of VHF
retrievals is the inability to retrieve the smallest drops, as the relevant
part of the precipitation spectrum is obscured by the clear-air. UHF profilers
are capable of retrieving smaller drops, but the clear-air echo is masked by
the precipitation peak in all but light rainfall. Correcting the precipitation
peak for vertical air motion is a crucial step in the retrieval process, and so
the clear-air information must be taken from a VHF profiler. Thus the
dual-frequency technique is capable of retrieving smaller drops, but suffers
the obvious fiscal drawback of requiring two co-located profilers. Based on a
modeling study, we have developed a VHF correction factor for small drops. The
first aim of the current study is to compare results obtained using this
correction factor, to those obtained using the dual frequency technique.
The
TWP-ICE field campaign was conducted in Darwin in January and February 2006.
During the campaign, the University of Adelaide operated a VHF Boundary Layer
Profiler, located on the ARM site at Darwin airport. At a field site 8 km to
the East, the Australian Bureau of Meteorology operated a VHF profiler,
co-located with a UHF profiler. All rain events which passed over the
University of Adelaide profiler during the campaign have been retrieved and
analysed. The same technique will be used to analyse some of the same rain
events using the Bureau of Meteorology profiler. These results can then be
compared to those obtained using the dual frequency system, and the small drop
correction examined. The second aim of this study is to use both VHF retrievals
to examine the evolution of the rain field over the 7 km spatial separation.
Initial results will be discussed.
Presented by: Dolman, Bronwyn
RASS
optimisation for mid-latitude summers
Andrew MacKinnon , Bronwyn Dolman , Lenard Pederick , Iain
Reid
University of Adelaide
The
University of Adelaide operates a Radio Acoustic Sounding System (RASS) at its
Buckland Park field site, used in conjunction with a 40 kW, 144 antenna 55 MHz
ST profiler. This RASS system consists of three large speakers each
individually power by a 1kW amplifier, with each speaker having an acoustic
output of over 130 dB. In early 2011, the RASS system was deployed to take
advantage of a 2 week field campaign at Buckland Park, which involved a
comparison between radar-derived wind profiles and 48 GPS sondes. RASS operated
for 5 minutes of every hour between 9 am and 5 pm LT, when a balloon was not in
the air. Dependent on the synoptic situation, virtual temperature profiles were
recovered from 500 m, to a maximum height between 1 and 5 km. The variation in
height coverage prompted a modeling study, which used ray tracing algorithms to
optimise the three speaker’s placements. The goal of which was to determine
optimal placement of the three speakers for a given month or season, depending
on horizontal wind patterns. Based on these findings, in early 2012, the
speakers were placed in an orientation optimal for the prevailing synoptics of
the South Australian Summer. A mini-campaign was then conducted, to examine
variations in height coverage, with speakers optimized for the season.
Results
from the original field campaign, the modeling study and the mini-campaign will
be presented.
Presented by: Dolman, Bronwyn
Planetary
wave activity during the summer months of 2007 over Gadanki
M.C. Ajay
Kumar 1, Gopa Dutta 2, et al.
1 Vanjari Seethaiah Memorial Engineering college
2 Vignana Bharathi Institute of Technology
Daily
wind data measured by MST radar at Gadanki (13.5o N,79.2o
E) during the summer months of 2007 have been analysed for planetary wave
activity in the altitude range of 3-20 km. Fourier Transform Technique (FFT)
has been applied to study the amplitude and frequency variations of these
oscillations. Strong peaks in zonal and meridional winds are found at 2.5 d, 4
d, 6.5 and 7.5-8.5d periods. A Kelvin wave of 12-15 d period is also seen in
zonal wind. The 7.5-8.5 d period wave is found to be most dominant both in
zonal (5.6 m/s) and meridional (2.75 m/s) winds at lower stratospheric heights.
The Kelvin wave shows maximum amplitude (5 m/s) at ~18 km. The ECMWF
Re-Analysis (ERA-Interim) wind data of approximately the same latitude –
longitude have been downloaded for the same period and similar analysis have
been carried out. The results obtained from radar data and ERA data show
striking similarity in period and structure of the waves. The squared-coherence
values between the two datasets in terms of cross-spectral amplitudes are found
to be highly significant.
Presented by: Dutta, Gopa
Response
of tropical lower atmosphere to annular solar eclipse of 15 January, 2010
Gopa Dutta 1, P. Vinay Kumar 1, M. Venkat Ratnam 2, Salauddin Mohammad 1, M. C. Ajay Kumar 3, P. V. Rao 4, H. Aleem Basha 5
1 Vignana Bharathi Institute of Technology, Ghatkesar, Hyderabad,
India.
2 National Atmospheric Research Laboratory,
Gadanki, India.
3 Vanjari Seethaiah Memorial College of
Engineering, Patancheru, Hyderabad, India.
4 Vasavi College of Engineering, Ibrahimbagh,
Hyderabad, India.
5 Moulana Azad National Urdu University, Gachibowli, Hyderabad,
India
Special
experiments were conducted with GPS radiosonde, ozonesonde and MST radar at two
tropical Indian stations Hyderabad and Gadanki during the annular solar eclipse
of 15 January 2010. Control observations in similar atmospheric conditions have
been compared with 15 January measurements to find the eclipse induced effects.
A
decrease in tropopause height is observed during and after the end of eclipse.
A fall/rise in temperature and ozone concentration is observed below/above the
tropical tropopause. Total ozone does not change during eclipse due to its long
life time, but its vertical distribution changes. Zonal wind shows significant
enhancements (~ 12-16 m/s) in both the stations confirming that the change is
due to the obscuration of the sun. Changes in meridional winds are not
appreciable.
Study
of short period (<2 h) gravity waves show clear enhancement of high
frequency (5-15 min) waves close to Brünt Väisälä period in the upper
tropospheric and lower stratospheric regions. Higher activity could be observed
after the beginning of the eclipse and persisted throughout the observation
period. A 40-60 min wave is found to be suppressed in north beam winds during
eclipse whereas a 25-35 min wave gets stronger in the east beam measurements.
The dynamical changes observed in this region could be responsible for the
redistribution of atmospheric species.
Presented by: Dutta, Gopa
Piracy,
maritime operations and radar-an overview in Nigeria
Aniekan
Ediang 1, Okuku Ediang 2, et al.
1 The Nigerian Maritime Administration and Safety Agency, NIMASA, 6
Burmal Road, Apapa, Lagos, Nigeria
2 Marine Division, Nigerian Meteorological Agency
Despite
the importance of the neigbouring oceans to the economics, climates and
biodiversity of many Africa Countries, the problems of managing successful
maritime safety and security along different coastlines still exist. The
research paper is intended to stimulate discussion and recommendations relating
to bridging the gap between maritime safety/Security and radar/global satellite
data as it relate to marine meteorological forecast in Nigeria and its role in
sustainable development in an African context. The paper recognizes that
National Meteorological Service (NMSS) must do more than simply pay up services
to sustainable development and must focus issues of relevance facing society in
area of marine meteorological forecast as it relate to maritime safety and security
along its coastal areas.
Presented by: Ediang, Aniekan
Taking
some advantage from a maritime accident and security along the coastline of
Gulf of Guinea via radar feed back management system
Okuku
Ediang 1, Aniekan Ediang, et al.
1 Nigerian Meteorological Agency, PMB1215 OSHODI LAGOS, Nigeria
This
paper gives a general overview of taking some advantage from maritime accident
and security along the coastline of Gulf Guinea via Radar feedback Management
System.
This
work aims at identifying that in West Africa, imagery from radar and satellites
observations do provide a mechanism for describing weather features such as
Cloud, Precipitation patterns and pressure systems. It’s possible to make
useful inference about the fields of wind flow.
The
rest of the paper is therefore organized first to consider radar is therefore
becoming increasingly important for long range planning with developing
countries. Secondly, concur that a next several endeavor’s to pinpoint certain
directions along which future research effort could bedirected for the rest of
the 21st century especially in radar as it relates to Maritime
Accident and Security along the Coastline of Gulf of Guinea.
Presented by: Ediang, Okuku
Investigations
on the variability of the tropical mesospheric echoes, winds, waves and
associated momentum fluxes
Sunkara
Eswaraiah 1, M. Venkat Ratnam 2, B.V. Krishna Murthy 3, S. Vijaya Bhskara Rao 1
1 Sri Venkateswara University, Tirupati-517502, India
2 National Atmospheric Research Laboratory (NARL), Gadanki,
Tirupati-517 502, India
3 B1, CEEBROS, Chennai-600020, India.
For
the present thesis work, an extensive long-term database (1998-2009) of
high-resolution Indian MST radar observations along with Rayleigh LIDAR
(1998-2008), GPS radiosonde (2006-2010) and M-100 rocket (1971-1991)
observations has been used. A campaign is also conducted during 13-17 January
2010 to address the eclipse effects on the middle atmosphere.
It
is observed that long duration (20-40 minutes and above 40 minutes) echoes
occurred mostly in 70-80 km altitude region and are highly sporadic in the
regions above and below it. Further, solar zenith angle dependence on the
duration of mesospheric echoes was found insignificant. Significant reduction
in the echo occurrence is found at the maximum epoch of the solar eclipse as
expected. Calculations of D region electron density during eclipse day and on a
normal day revealed that background electron density on a normal day prevailing
at ~0700 hrs IST existed during solar eclipse maximum obscuration time. High
frequency gravity waves close to the eclipse path are detected in the
troposphere and mesosphere which is not expected.
The
observed mesospheric vertical winds are generally upward in all the seasons.
The vertical wind can reach occasionally values as high as 5 ms-1 but
most of the time (95%) it is, in general, less than ~2.63 ms-1. The
present observations are consistent with the general circulation features in
recent models for low latitude locations with northward and upward wind
prevailing throughout the year representing part of meridional circulation.
Though there is a difference in the wind magnitude between MST radar
observations and the model, the trends match well particularly between 70 km
and 75 km.
The
variability in the momentum flux from troposphere to mesosphere associated with
the gravity waves of periods 20 min. to 2 h is also investigated. An effort is
also made to examine the variations in momentum flux for different cases, viz.,
during the occurrence of mesospheric temperature inversion and convection
events. Interestingly, the vertical flux of zonal momentum estimated from lidar
is in the range of those estimated from radar data in the overlap altitude
region, though the estimates are from two different techniques. In summer large
variations with altitude in mesospheric zonal momentum flux are noticed with a
magnitude ~0- 4 m2/s2. The meridional fluxes in the
mesosphere are higher in equinoxes (~10-12 m2/s2). This
study will help in better understanding the dynamical aspects of tropical
mesosphere using VHF radar observations.
Presented by: Eswaraiah, Sunkara
Advances
in science and techniques of mesosphere, stratosphere, and troposphere (MST)
radar
Shoichiro Fukao
Fukui University of Technology/ Research Institute for Sustainable
Humanosphere, Kyoto University
Atmospheric
radars generally called MST (mesosphere, stratosphere, and troposphere) radars
or ST radars are, with certain limitations, capable of remotely and
continuously sensing three-dimensional winds, waves, turbulence, and
atmospheric stability over the wide altitude range 1-100 km in the Earth’s
atmosphere. In particular, direct measurement of vertical wind velocity over
such a wide altitude range is possible only with MST radars. Their time
resolution of about 1 min and altitude resolution of 75-150 m are unequalled by
conventional instruments (e.g., rawinsondes and rocketsondes), making it
possible for MST radars to quantitatively investigate the small-scale
atmospheric gravity waves that are considered to play important roles in the
dynamics of the Earth’s atmosphere. Recently, range imaging modes with multiple
carrier frequencies have been incorporated in atmospheric radars for an
extensive study of micro-scale Kelvin-Helmholtz instabilities and other
small-scale processes in the upper troposphere and lower stratosphere.
In
the last four decades, this excellent capability has been extensively used to
study various dynamical disturbances in the Earth’s atmosphere and ionosphere,
developing new frontiers of atmospheric research on, primarily, mesoscale and
micro-scale phenomena. In the present talk, these advances including
application to the practical weather forecast are briefly reviewed.
Presented by: Fukao, Shoichiro
Structure
and dynamics of air inhomogeneities in the environment of a cirriform cloud
from balloon and high-resolution radar measurements
Hubert Luce 1, Shoichiro Fukao 2, Masayuki K. Yamamoto 3, Hiroyuki Hashiguchi 3, Tomoaki Mega 4, Takuya Tajiri 5, Masahisa Nakazato 6
1 South Toulon-Var University, La Garde, France
2 Department of Space Communication Engineering, Fukui University of
Technology, Japan
3 Research Institute for Sustainable Humanosphere, Kyoto University,
Japan
4 Division of Geophysics, Graduate School of Science, Kyoto
University, Japan
5 Meteorological Research Institute, Tsukuba, 305-0052, Japan
6 Japan Meteorological Agency, Tokyo, Japan
The
vertical structure of clouds and air inhomogeneities and their time evolution
can be directly measured by vertically pointing radars. This information is
generally inferred from aircraft paths, but only at different altitudes and
different times, with a time spacing much larger than the span life of the
cloudy and clear air structures. Consequently, co-located ground-based cloud
and clear air radars are a unique combination of tools for getting some
insights into cloud thermodynamics and interaction with their environment.
In
October/November 2008, a multi-instrumental experiment was conducted at
Shigaraki MU observatory, including the VHF MU radar (mainly sensitive to air
refractive index irregularities) in range imaging mode (resolutions: ~several
ten meters, ~20 s) and a Ka-band (35.25 GHz) cloud radar sensitive to
hydrometeors (resolutions: 50 m, 20 s).
On
11/12 November 2008, cirrus and fallstreaks were monitored by the Ka-band radar
above the altitude of 7.3 km. The time-height cross-section of equivalent radar
reflectivity revealed convective cloud cells developing at the top of a
stratiform cloud layer up to 9.0 km. The convective nature of these structures
was supported by the observation from the MU radar of upward air velocities
inside the cells and by the identification from balloon data of a conditional
instability in their altitude range. Downward air motions were observed between
and around the top of the cells. In addition, the cloudy cells were associated
with complex features in MU radar echoes: in particular, time-height cross-section
of MU radar echo power showed enhancements between the cloud
cells (appearing as vertical striations in the images) with maxima at their
base. Interpretations of these original observations will be given.
These
results support the high potentials of combining high resolution ST radars with
cloud radars for investigating cloud dynamics at small scales.
Acknowledgement:
This
study is supported by the Ministry of Education, Culture, Sports, Science and
Technology of Japan under the program of Special Coordination Funds for
Promoting Science and Technology, “Japanese Cloud Seeding Experiments for
Precipitation Augmentation (JCSEPA)”. We thank Takashi Ichiyama and Yuji
Ohhigashi of Mitsubishi Electric TOKKI Systems Corporation for providing
Ka-band radar.
Presented by: Fukao, Shoichiro
Monitoring
and data assimilation of Wind Profiler
Catherine
Gaffard 1, David Simonin 1, Colin Parrett 1, Richard Marriott 1, Dirk Klugmann 1, David Hooper 2
1 UK Met Office
2 STFC Rutherford Appleton Laboratory
The
monthly monitoring against model data show that wind profilers are giving wind
with an accuracy comparable to radiosonde wind measurements. The wind profiler
winds have been assimilated as radiosonde winds with an error which varies with
height but is independent of the site. Variation in quality exists between wind profilers due to contamination associated with specific
site (ground clutter, sea clutter, RFI, aging of the antenna). As a first
approximation and because when the error exceed a certain threshold wind
profilers are blacklisted automatically, the use of non site dependent error is
valid. However different wind profilers have different vertical resolutions and
a better error characterisation should improve the assimilation of the wind
profiler.
In this paper we show some results of the operational monitoring. We will
present very preliminary results on adjoin tools sensitivity and show the
potential use of such technique to improve the blacklisting process. We look in
more detail at the observed quantity and its equivalent model. In particular we
show how wind profiler winds are actually used in the UK Met Office UM. One
example of wind profiler data assimilation and forecast impact in the very high
resolution model (1.5km) is presented.
Presented by: Gaffard, Catherine
Radar
observations of the Perseid meteor shower activity and meteoroid stream
structure from the Gadanki MST radar
Yellaiah Ganji , K. Chenna Reddy
Osmania University, Hyderabad
We
report the results of our study of Perseid meteoroid stream mass distribution
from the shower activity during the year 2004 – 2010 recorded at the Gadanki
(13.46o N, 79.18o E) MST radar. The distribution of
meteor signals reflected from backscatter radar is considered according to
their duration.This time duration (t) is used to determine the relative flux of
the shower in different particle size ranges producing different classes of
echoes with duration intervals t <0.4 s, t = 0.4 – 1.0 s and t ≥1.0 s.
From this duration classes, mean activity curves are determined for different
sizes of the meteoroid particles of the stream.The averaged value of mass index
(s) is 1.67±03 on the peak day of the shower activity. It is sheen that the
particle mass distributions are qualitatively same along the entire orbit of
the stream. Activity profiles in three echo durations categories are slightly
differ in the position of the peak activity which range in the solar longitude
of 1390 ≤ λo ≤ 1400.5
(J2000.0). The mean activity profiles are showing a systematic change withwax
and wane in the strength of the shower outburst.
Presented by: Ganji, Yellaiah
'Sky
noise’ temperature recorded by the UK MST radar at 46.5 MHz
Ivan Astin
1, Bala Goudar 1, David Hooper 2
1 University of Bath
2 Rutherford Appleton Laboratory
We
present a study of 'sky noise', that has been recorded
by the UK MST radar on a quasi-continuous basis since 1997. This data is
routinely used to derive SNR. However, it hasn’t been the subject of serious
study, even though it can be used for long-term system performance monitoring
and calibration. There was, however, a short study made in the early 1990s by
the University of Sheffield who (in an unpublished report) used signals from
the radio source Cassiopeia-A to show that the one of the UK MST radar beams
(NE6) was within 0.1º of its nominal pointing direction. We repeat this study
here, and show that there has been little change in the beam pointing angle
over the 20 years since then. The only change is that the noise power (at a
given right ascension and declination) fluctuates by 1-2 dB over time, due to
ionsopheric absorption (with the radar acting as a riometer). We also show that
both Cassiopeia-A, and Cygnus-A, can be clearly seen by other beams not
considered in the Sheffield study, and provide a radio ‘map’ of the sky at 46.5
MHz covering 24 hours of right ascension and declination from 41º to 60º North.
We compare our results to those of Campistron et al. (2001)*, who
produced a similar map at 45MHz using five ST radars in Continental Europe.
*B.
Campistron, G. Despaux, M. Lothon, V. Klaus, Y. Pointin, and M. Mauprivez
(2001), ‘A partial 45 MHz sky temperature map obtained from the observations of
five ST radars’, Annales Geophysicae 19: 863–871
Presented by: Goudar, Bala
Adaptive
suppression of aircraft clutter with the PANSY radar training system
Taishi
Hashimoto 1, Koji Nishimura 2, Kaoru Sato 3, Toru Sato 1
1 Kyoto University
2 National Institute of Polar Research
3 The University of Tokyo
PANSY
(Program of Antarctic Syowa MST/IS Radar) is a project to construct a large
atmospheric radar at Antarctic Syowa Station. PANSY is the first MST radar in
the Antarctic region that is the only instrument capable of continuously
monitoring three-dimensional structure of the air in high altitude and time
resolutions, and thus is expected to substantially progress the polar
atmospheric science. PANSY has two antenna arrays, large main array with 1045
Yagi antennas and smaller one towards the direction of the magnetic south pole for the observations of FAI (Field Aligned Irregularity).
Although
FAI echoes are of great scientific interests, they can be interferences for the
observation of ionospheric incoherent scattering around 100 km, so we must
arrange a countermeasure in advance.
Ahead
of the construction of PANSY, a training system named "Sumire" had
been set up in Shigaraki MU Observatory, Japan. There is a
busy air traffic around the observatory, and their clutter has been the
pending problem in the atmospheric observations of the MU radar.
Aircraft
clutters are similar to FAI echoes in that they are both strong backscattering
from rapidly moving objects, but it is less complicated because of its linear
movement. For the aircraft clutter suppression with atmospheric radar, a
combination of DCMP-CN (Directionally Constrained Minimization of Power with
Constraint of Norm) and DOA (Direction Of Arrival)
estimation has been suggested. The approach is as follows. First we estimate
the DOA of aircraft clutter. Then we add a directional constraint to DCMP-CN to
create a null at that direction.
In
this presentation, we first show the result of applying this method against the
aircraft clutters using two different systems, Sumire and the MU radar, and
then discuss the relationship between the effectiveness and the size or shape
of the array. While Sumire has only 4 channels with different sizes, MU radar
has 25 channels of almost equal sizes. DCMP-CN keeps the shape of main robe
using directional and norm constraint, so the remaining degrees of freedom and
the location of each channel determine the performance of this method.
Finally,
we suggest a selection of channel for the better FAI clutter rejection in
PANSY.
Presented by: Hashimoto, Taishi
Radar
investigations of mesospheric clouds subjected to artificial electron heating–
observations and theory.
Ove Havnes 1, Cesar La Hoz 1, Alexander Biebricher 2, Meseret Kassa 1, Jörg Gumbel 3
1 Institute of Physics and Technology, University of Tromsø, N-9037
Tromsø, Norway.
2 Andøya Rocket Range, Box 54, N-8483 Andenes,
Norway.
3 Department of Meteorology, Stockholm
University, S-10691 Stockholm, Sweden.
It
has for some time been known that artificial heating of the mesospheric clouds
PMSE/NLC and PMWE can have a profound effect on their radar backscatter
properties. In some cases the backscatter can be reduced by a large factor as
the heater transmitter is switched on and, if the heater cycling is asymmetric
with a comparatively short heater on time but with a much longer heater off
time, the backscatter can increase as the heater is switched off, to a value
which can be several times its undisturbed value from before the heater was
switched on. This effect is called the overshoot effect and the shape of its
variation during the heater cycling is, with present modeling, very dependent
on the dusty plasma conditions in the radar clouds. We present observations of
the overshoot for PMSE and PMWE clouds. We discuss how the observations of the
backscatter variation compare with modeling which predict a possibility for
significant changes in the overshoot behavior when the radar frequencies
becomes lower than ~ 50 MHz. We finally present some recent rocket results of
dust structures in PMSE clouds and their possible significance for the shape of
the dusty plasma irregularities causing the radar backscatter.
Presented by: Havnes, Ove
Measurements
of wind variation in surface boundary layer with tilted 1.3GHz wind profiler
Kuniaki Higashi , Jun-ichi Furumoto , Hiroyuki
Hashiguchi
Research Institute for Sustainable Humanosphere (RISH), Kyoto University
This
study aims to elucidate the effects of local wind field in the surface boundary
layer. In this study, tilted 1.3 GHz wind profiler and fine mesh numerical
model are used to investigate behavior of wind field and large eddy in the
layer. The wind and large eddy are changed in a short time, and warm or cold
air is mixed near surface. These are important parameter to understand lower
troposphere phenomena. Many studies depend on tower observations; therefore it
is not understand widely distribution of changing wind in surface boundary
layer. In this study, to reduce the minimum height of observation, the antenna
of the wind profiler is tilted from the ground surface. Three radar beams are
used to observe radial wind in the boundary layer. It is appear to non-uniform
system.
We
also use the fine mesh numerical model called Large Eddy Simulation. The domain
of this numerical model is from several meters to several kilometers, and can
predict the airflow over complex terrain with high precision. Model domain used
50 m resolution topography data. This topography data was provided from
Geospatial Information Authority of Japan. We compared simulation and
observation result to appear the phenomena of the surface boundary layer.
Presented by: Higashi, Kuniaki
Development
of turbulence detection and prediction techniques with wind profiler radar for
aviation safety
Hiroyuki
Hashiguchi 1,
Kuniaki Higashi 1, Seiji Kawamura 2, Ahoro Adachi 3, Yusuke Kajiwara 4, Kotaro Bessho 4, Masanobu Kurosu 5, Mamoru Yamamoto 1
1 Research Institute for Suatainable Humanosphere (RISH), Kyoto
University
2 National Institute of Information and Communications Technology
(NICT)
3 Meteorological Research Institute (MRI), Japan Meteorological
Agency (JMA)
4 Observation Division/Meteorological Research Institute (MRI),
Japan Meteorological Agency (JMA)
5 Japan Airlines (JAL)
There
are various meteorological phenomena which may cause serious trouble to
aircraft operations. Especially, atmospheric turbulence (including wind shear)
sometimes brings significant aircraft accidents because it is difficult to
detect it by current operational meteorological observations. In 2000-2009,
more than half of accidents in large aircrafts were brought by atmospheric
turbulence. At present, PIlot weather REPort (PIREP) is a major method for
observing atmospheric turbulence, but it is not suitable for monitoring
atmospheric turbulence because it cannot continuously observe a specific area
or altitude. Therefore, the development of a new observation instrument, which
continuously covers wide altitude range, is needed. On the other hand, various
forecast techniques for atmospheric turbulence have been developed based on
PIREP data, so there is still room for improving its prediction accuracy.
The
project supported by 'the Program for Promoting Fundamental Transport
Technology Research of the Japan Railway Construction, Transport and Technology
Agency (JRTT)' started in July 2011. In the present study, the prototype of the
next generation 1.3-GHz wind profiler radar (WPR) that can be observed up to
the cruising altitude of the aircraft is developed, and it aims at the
establishment of the atmospheric turbulence detection technique by the remote
sensing. In addition, the observational data with the WPR is used as
verification data to improve the prediction accuracy of atmospheric turbulence.
It aims to become the foundation of the aircraft accident prevention.
It
is expected that the result achieved by the present study will be built into
the WPR network of Japan Meteorological Agency (JMA) for the meteorological
observations. In addition, it is expected to contribute to a safe service of
the aircraft operation through the improvement of the prediction accuracy for
atmospheric turbulence.
Acknowledgments: The present study was supported by the Program for Promoting
Fundamental Transport Technology Research from the Japan Railway Construction,
Transport and Technology Agency (JRTT).
Presented by: Higashi, Kuniaki
Recent
advances in radar turbulence studies with emphasis on in-situ comparisons
Wayne
Hocking, Arnim
Dehghan
T.B.D.
Presented by: Hocking, Wayne
Good
resolution at high power without pulse-coding
Wayne
Hocking 1, Anna Hocking 2
1 University of Western Ontario
2 Mardoc Inc.
Pulse
coding is currently the most common procedure used to produce fine height
resolution with high power. However, new developments with radar processor
design have permitted better approaches to data-recording and analysis. Using
several multi-core CPUs, we have been able to achieve speeds of up to 40GHz
from a standard commerical motherboard, allowing data to be digitized and
processed without the need for any type of hardware except for a transmitter
(and associated drivers), a receiver and a digitizer. No Digital Signal
Processor chips are needed, allowing great flexibiltiy with analysis
algorithms.
As
a result of these advances, we have been able to re-address the modes of
optimal pulse compression. Pulse coding requires that the sampling interval must
match the timing between successive sub-elements of the pulse, but our newer
procedures allow direct sampling of the RF, permitting alternative stategies
such as chirped pulses, and even pulse shape variations from pulse to pulse.
Real-time deconvolution with the transmitted pulse permits optimal resolution,
and can even remove range-ambiguity effects in high PRF systems.
These
new developments are discussed and demonstrated with examples.
Presented by: Hocking, Wayne
Incorporation
of O-QNet windprofiler data into numerical forecast models
Wayne
Hocking 1, Peter Taylor 2, Frederic Fabry 3, James Drummond 4, et al.
1 University of Western Ontario, Canada
2 York University, Canada
3 McGill University, Canada
4 Dalhousie University, Canada
Canada
now has 10 active windprofiler radars - 8 as part of the O-QNet, 1 additional
one in Montreal at McGill University, and one at Eureka in the high Arctic. An
extra 3 are slated for incorporation in the next year. The O-QNet is particularly
of interest, since it is a relatively dense network (mean spacing between
radars less than 200km), and of course the high Arctic is a region of special
interest for forecast models.
Data
from each of these are now routinely submitted to Environment Canada and
E-WINPROF servers, for study and incorporation into forecast models. The
process by which this has occurred is an interesting one, and has not been at
all trivial. Computer models for data assimilation and prediction are now very sophisticated,
and other sources of data like aircraft (AMDAR) are very competitive. Radar
data do not always produce a positive improvement in the models, and care is
needed both from the perspective of the radar operator(s) and those receiving
the data. Misunderstandings can lead to conflict. High accuracy is required,
requiring compensation for anisotropy effects, and care with near-0-Hz spectral
lines (due to ground echoes)
In
this talk, we will discuss the history of the assimilation process, and some of
the adjustments needed to optimize it.
Presented by: Hocking, Wayne
Annual
and interannual variations of mesospheric gravity waves from radar, satellites
and models
Peter
Hoffmann 1, Manfred Ern 2, Erich Becker 1, Peter Preusse 2, Markus Rapp 1
1 Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock
University, Kühlungsborn, Germany
2 Institute for Energy and Climate Research – Stratosphere (IEK-7),
Forschungszentrum Juelich, Juelich, Germany
Wind measurements with meteor and MF radars at Juliusruh (55°N, 13°E) and
Andenes (69°N, 16°E) are used to estimate annual and interannual variations of
the activity of gravity waves (GW) in the mesosphere/lower thermosphere (MLT).
The derived results at both locations are compared to high spatial resolution
data sets of temperature variations derived from the satellite instrument SABER
as well as to the simulated annual cycle using the gravity-wave resolving
Kühlungsborn Mechanistic general Circulation Model (KMCM). These data are used
for comparison between single ground based observations and zonally averaged
results. Observational and computational results show the largest GW energy
during winter and a secondary maximum during summer. This semi-annual variation
is consistent with the selective filtering of westward and eastward propagating
GWs by the mean zonal wind. The latitudinal dependence during summer is
characterized by stronger GW energy between 65 and 85 km at mid-latitudes than
at polar latitudes, and a corresponding upward shift of the wind reversal
towards the pole. Based on long term measurements of mesospheric wind
variations at mid and polar latitudes and temperature variations from SABER
observations, the interannual variations of the activity of GW with different
periods and their dependence on the background winds are investigated. First
results indicate that observed zonal wind variations at about 75 km during
summer at mid-latitudes go along with an enhanced activity of GW with periods
between 3 - 6 hours at altitudes between 80 and 88 km. We will continue our
studies of GW variations for other seasons at both latitudes to illuminate the
contribution of the selective GW filtering by the background winds.
Presented by: Hoffmann, Peter
Renovation
of the Aberystwyth MST radar: Evaluation
David
Hooper 1, John Bradford 1, Les Dean 2, Jon Eastment 1, Marco Hess 3, Eric Hibbett 3, John Jacobs 4, Richard Mayo 3
1 Rutherford Appleton Laboratory
2 Aberystwyth University
3 ATRAD
4 John Jacobs Consulting
In
early 2011, the Aberystwyth MST Radar underwent its first major renovation in
its 20 year lifetime. This principally consisted of replacing the components
which allow it to operate according to the Doppler Beam Swinging principle. The
design and installation work was carried out by ATRAD. The renovation
lead to a remarkable 28% increase in useful coverage for wind-profiling
purposes. This presentation will look at how the performance of the renovated
radar was evaluated using geophysical considerations.
For 2 weeks prior to the renovation work, the radar was operated in a special
observation format which made use of all 16 of the available beam pointing
directions. Only 6 of these are used during standard operations. The special
format continued to be used for 6 weeks after the renovation was completed.
After several days’ worth of observations had been accumulated, it was possible
to analyse the diurnal variations of spectral noise power. For each beam
pointing direction, there should be a specific pattern which follows the
variations in 46.5 MHz cosmic emissions along a circle of constant declination.
Although the patterns for the pre and post renovation periods were
qualitatively well-matched, there was a decrease in the absolute values by
approximately 1 dB, suggesting a decrease in system noise.
After several weeks’ worth of observations had been accumulated, it was
possible to carry out a statistical analysis of the data products. It was
immediately obvious that the ratio of signal powers for observations made in
the vertical direction and at 6 degrees off-vertical, i.e. nominally a measure
of the aspect sensitivity, had decreased. The values are expected to be small
throughout much of the troposphere, where isotropic scattering is a common radar
return mechanism. This was only the case for the post renovation period. This
suggests that the old relay units were causing considerably more attenuation
for off-vertical beam pointing directions than for the vertical direction. The
difference is estimated to be 5 dB. Moreover, the aspect sensitivity parameter
theta_s is used to compensate the horizontal wind speeds for the difference
between the nominal and effective beam pointing zenith angles. It is estimated
that wind speeds were being over-compensated by 6% prior to the renovation.
Independent data quality statistics provided by the Met Office suggest an
improvement for the post renovation period.
Presented by: Hooper, David
The
usefulness of model-comparison statistics for wind-profiling radar operators
David
Hooper
Rutherford Appleton Laboratory
Wind-profiler
radar data are commonly assimilated by meteorological organisations for the
purposes of numerical weather prediction (NWP). Within Europe, the radars are
operated by a variety of organisations. Nevertheless, they effectively form a
single network through the co-ordination of the EUMETNET Composite Observing
System (EUCOS) E-WINPROF programme. This grew out of the CWINDE demonstration
network, which was set up under COST-76. As part of E-WINPROF, the quality of
the radar-derived wind data is evaluated through comparisons with NWP model
data. This presentation will look at the usefulness of such model-comparison
statistics from the instrument operators' perspective. They can be used to
evaluate improvements in signal processing schemes and to identify changes in
instrument performance.
The (UK) Met Office generate statistics from
comparisons made against their own NWP model. These are provided on a monthly
basis as functions of model level, i.e. of altitude. Owing to the fact that NWP
models are not perfect, the differences between radar-derived and model winds
cannot be attributed solely to errors in the radar data. Nevertheless, if two
sources of data have similar model-comparison statistics, it can be inferred
that their measurement accuracies are broadly comparable. Consequently, for
each wind-profiling radar, the Met Office also provide
model-comparison statistics for radiosonde data from the same geographical
region. The combined statistics have been of particular usefulness for the
Aberystwyth MST radar in two specific circumstances. Firstly, they were used to
demonstrate that an improved signal processing scheme gave data of
significantly higher quality than its predecessor. Secondly, they were used to
identify a problem with a new data acquisition system. The cause turned out to
be a range gating error.
EUCOS generate statistics from comparisons made against the Deutscher
Wetterdienst (DWD) COSMOS model. Data quality is summarised by a single value,
which covers all model levels and times. As for the case of Met Office
statistics, the evaluation period is typically 1 month. However, single day
statistics are also available. These have proved to be particularly useful for
identifying quality control problems which are confined to limited time and
altitude regions. Such problems can otherwise be difficult to identify and to
correct.
Presented by: Hooper, David
Predicting
the occurrence of visual noctilucent clouds
John
Rowlands 1,
Nicholas Mitchell 1,
David Hooper 2
1 University of Bath
2 Rutherford Appleton Laboratory
This
work is motivated by the needs of an amateur noctilucent cloud (NLC)
observation network at northern mid-latitudes. The level of public interest in
NLCs has been raised considerably after one of us (Rowlands) participated in a
BBC Radio popular science programme. Although NLCs are commonly seen above the
British Isles during the twilight hours of June and July, it would be useful to
know in advance, even if only by a few hours, which nights are likely to offer
the best observations. This work is not concerned with the effects of
tropospheric clouds, despite the fact they have a dominating influence on
whether or not NLCs might be visible. It focuses on the temporal relationships
between NLC occurrence and low mesopause temperatures, as measured by a meteor radar, and between NLC occurrence and mesosphere
summer echo (MSE) occurrence, as measured by an MST radar.
Visual observations were made on a nightly basis, when the sky was not obscured
by tropospheric cloud, during June and July of each year 2009 - 2011. The
observation site (53.42 N, -4.45 E) is characterised by low levels of light
pollution and flat terrain in all directions. The horizon between west and east
through north is over the sea.
Mesopause-level temperatures were derived from the University of Bath's
(SKYiMET) meteor radar at Esrange in Northern Sweden (67.89 N, 21.08 E) degrees
E). Despite its large (principally meridional) separation from the NLC
observation site, there is a reasonable correlation between the occurrence of
extensive NLCs (i.e. when the extent rose more than 15 degrees above the
horizon) and cool phases of the 5 day planetary wave.
The study is now being extended to include mesopause-level information from a
more-local source. The Aberystwyth MST radar (52.42 N, -4.01 E) is located just
115 km to the south of the NLC observation site. It commonly observes daytime
MSEs during June and July of each year. The relationship between the occurrence
of MSEs and the existence of ice crystals in the uppermost mesosphere is
well-established. An initial comparison has revealed that the the most
extensive NLC display of the 2011 season occurred during the night following
the most extensive MSEs.
Presented by: Hooper, David
Detecting
low earth orbit (LEO) satellites using UK-based atmospheric radars
Jon Eastment , David Hooper , Darcy Ladd , Chris Walden
Rutherford Appleton Laboratory
Owing
to the rapidly-increasing use of the near-Earth space environment, there is a
growing need to be able to detect the objects within it. This is primarily
motivated by the threats posed to operational satellites, and to manned
spacecraft, by collisions with orbital debris or with other satellites. A
dedicated space surveillance radar network already exists for this purpose.
Nevertheless, due to the ever-increasing number of objects which must be
tracked, there is considerable interest in how additional radars, which were
designed for other purposes, might also contribute. For example, it has already
been demonstrated that the MU radar in Japan is capable of detecting LEO
objects. This poster will examine the suitability of two UK-based atmospheric
radars for the same purpose: the Chilbolton Advanced Meteorological Radar
(CAMRa) and the Aberystwyth MST Radar.
CAMRa is a 3 GHz system which uses a 25 metre diameter parabolic dish, which
can be steered at 3 degrees/s in azimuth and 1 degree/s in elevation.
Consequently, it is able to continuously track objects, based on their known
orbits, as they move across the sky. Under a recent ESA-funded observational
campaign, the radar successfully tracked over 40 satellites in LEO at ranges up
to 2500 km. The missions of these satellites included communications (IRIDIUM);
weather observation (METOP-A, FENGYUN-3A, FENGYUN-3B); remote-sensing research
(ADEOS, AQUA, TERRA); earth observation (ENVISAT, RADARSAT-1, SPOT-5); and
military/intelligence (COSMOS_1346, COSMOS_1782, GEO-IK-2). Objects
with radar cross-sections (RCSs) as low as 2 square-metres (+3 dBsm) were
detected at 1000 km range (for example, CRYOSAT-2).
The Aberystwyth MST Radar is a 46.5 MHz system with a phased-array antenna.
Owing to its 20 year old radar control and data acquisition system, the maximum
inter-pulse period is currently only 640 us. This corresponds to a maximum
unambiguous range of 96 km. At this proof-of-concept stage, it will be
necessary to rely on range-aliased signals. Tests will initially be made using
the International Space Station (ISS), which occasionally passes close to the
centre of one of the radar's beam-pointing directions. At the time of writing,
the altitude of the ISS orbit varies between 375 and 404 km. If initial
observations of the ISS prove successful, the radar will be tested against a
set of satellite targets with progressively lower RCSs, so as to establish the
limits of its sensitivity and of its range and angular coverage.
Presented by: Hooper, David
Higher
application of wind profilers to forecasting/nowcasting severe convections and
to aviation weather services
Masahito
Ishihara
Aerological Observatory
The
wind profiler network of the Japan Meteorological Agency (JMA), WINDAS was stablished
in 2001 as the third nation/region-wide operational wind plofiler networks
following the U.S. NOAA Profler Networok and the EUPROF. WINDAS consists of 31
sets of 1.3GHz wind profilers covering through the whole area of Japan from 24N
to 44N. WINDAS has been providing upper-air wind data for mainly the JMA
mesoscale numerical model the using 4-dimenisonal variational data assimilation
method as well as daily weather serviceis and aviation weather serviceis. It
has also been contributed to researches mainly on mesoscale severe convections
and typhoons. JMA has started a research project to develope higher application
of the wind profilers to forecasting/nowcasting severe convections and to
aviation weather services. The project is being conducted in cooperation with
the Kyoto University and the National Institute of Information and
Communications Technology. The review of the history of the WINDAS and the
on-going project will be presented.
Presented by: Ishihara, Masahito
Long-term
trends of mesosphere/lower thermosphere gravity waves at midlatitudes
Christoph
Jacobi 1, Peter Hoffmann 2
1 Universität Leipzig
2 Leibniz-Institute of Atmospheric Physics
Mesosphere/lower
thermosphere (MLT) winds over Germany measured with different radar systems (MF
radar, LF) have been analysed with respect to variations at the time scales of
gravity waves. Background winds are also registered to analyse gravity-mean
flow interactions at decadal time scales. A decreasing (towards more westward
directed) zonal mean wind long-term trend is observed in the summer mesosphere
over Collm since 1984, which decreases with altitude and eventually reverses.
The gravity wave proxy trends show opposite tendencies, i.e., decreasing mean
zonal winds are connected with increasing gravity wave amplitudes and vice versa.
This behaviour can be explained through linear theory: since in summer
decreasing/increasing zonal westerly winds are connected with a stronger/weaker
mesospheric easterly jet, this leads to larger/smaller intrinsic gravity wave
phase speeds and consequently larger/smaller gravity wave amplitudes. This
connection between gravity waves and mean wind is also observed on a decadal
scale: during solar maximum a stronger mesospheric zonal wind jet leads to
larger gravity wave amplitudes. This results in a solar cycle modulation of
gravity waves with larger amplitudes during solar maximum. The results are
compared with MF radar trend results over Juliusruh.
Presented by: Jacobi, Christoph
Climatology
of the 8-hour solar tide over Central Europe, Collm (51.3°N; 13.0°E)
Christoph
Jacobi , Tilo
Fytterer
Universität Leipzig, Institut für Meteorologie
The
horizontal winds in the mesosphere and lower thermosphere (MLT) at 80-100 km
height have been measured using an all-sky 36.2 MHz VHF meteor radar at Collm,
Germany (51.3°N, 13°E). The radar has been operating continuously since July
2004, and data from 2005 – 2011 areused for constructing a
climatology of the 8-h solar tide. The 8-hour solar tide is a regular
feature; its amplitude shows a seasonal behaviour with maximum values at the
equinoxes, and generally increasing with altitudes. The largest amplitudes are
measured in autumn, reaching up to more than 15 m/s, while the tide is much
weaker during summer. The phase, defined as the time of maximum eastward or
northward wind, respectively, is earlier in winter and advances to later times
in summer. In general, the phase difference between the zonal and meridional
components is close to +2h. The vertical wavelengths are short in summer (<
30 km) but significantly longer during the rest of the year. The terdiurnal
tide is generally assumed to partly originate from non-linear interaction
between the diurnal and semidiurnal tide. Correspondence between semidiurnal
and terdiurnal amplitudes is investigated.
Presented by: Jacobi, Christoph
Study
of radar bright band and freezing level height
Rajasri
Sen Jaiswal,
R. Fredrick Sonia 2,
V. S. Neela 2,
M. Rasheed 2,
Zaveri Leena 2,
V. Sowmya 2
1
2 Sona College of Technology
Radar
bright band is a very important factor in identifying the type of
precipitation. A stratiform precipitation is generally found to be associated
with bright band1,2, while no bright band
is seen in convective precipitation1,2. During a precipitation
process, when the falling ice particles reach below the transition height, then
they start melting and form water coated snowflakes which produce a strong
signal in the radar receiver, giving rise to what is called a bright band.
Thus, knowledge of radar bright band is essential in understanding the
precipitation process. A bright band occurs because of the strong signal
reflected from the water coated ice particles below the 0o C
isotherm height. At above 10 GHz these snowflakes may lead to attenuation of
the signal. Hence, study of bright band is of immense importance in
communication also.
It
is realized that the atmospheric dynamics over the continent are different from
that over the ocean3. Hence, it appears that the parameters
associated with the bright band will also be different over land and ocean. In
this paper the authors have made an attempt to study bright band height (BBH),
bright band intensity (BBI) and freezing level height (HFL) within the
latitudinal belt 30N-30S during 1999-2002 and 2007. The BBH and BBI data are
derived from the level 2 data product 2A23 of the precipitation radar (PR)
onboard Tropical Rainfall Measuring Mission (TRMM) satellite. The study
presents statistics of BBH, BBI and HFL; the geo location of maximum occurrence
of bright band and the geo location of BBH maxima and minima. It is found out
that the BBH maxima mostly lie over land, while the minima lie mostly over
ocean. HFL shows strong latitudinal dependence. BBH is found to occur mostly below
HFL. However, in some cases, the reverse is found true. It is further found
that over the continent, there is strong correlation between latitude and the
percentage of time BBH goes above HFL.
Reference
3.
McGregor R and Nieuwolt S, Tropical climatology, Second Edition, Wiley, pp.339,
1998.
Presented by: Jaiswal, Rajasri
Sen
Active
modification of the D-region ionosphere
Antti Kero
Electron
temperature dependent properties of the D-region ionosphere can be actively
modified by means of radio wave heating. In propagation through weakly-ionised
collisional plasma, part of radio wave energy is deformed into thermal motion
of the electrons gas in elastic collisions of electrons, oscillating along the
radio wave, and neutrals. The D-region ionosphere is an optimal place for this
process since high electron-neutral collision frequency and significant
abundance of free electrons. A powerful radio transmitter, such as EISCAT
Heating facility, is therefore capable of increasing the electron temperature
in the D-region ionosphere by a factor of 5-10.
The
enhanced mobility of heated electron gas affects directly into the ion
chemistry via two competing processes, i.e. (decreased) recombination and
(increased) attachment rate. According to the Sodankylä Ion Chemistry model
(SIC), the enhanced electron attachment to neutrals, producing negative ions
and reducing the electron density, dominates typically below 80 km, whereas
above the reduced recombination increases slightly the electron concentration.
In this presentation, possible heating induced ion-chemical signatures in
incoherent scatter radar observations are discussed.
Presented by: Kero, Antti
The
MU radar meteor head echo analysis technique and the 2009-2010 observation programme
Johan Kero 1, Csilla Szasz 2, Takuji Nakamura 3, David Meisel 4, Toshio Terasawa 5, Yasunori Fujiwara 6, Masayoshi Ueda 6, Koji Nishimura 3, Jun-Ichi Watanabe 7
1 Umeå University, Kiruna, Sweden
2 SSC Space, Kiruna, Sweden
3 National Institiute of Polar Research (NIPR), Tokyo, Japan
4 SUNY Geneseo, NY, USA
5 Institute for Cosmic Ray Research, University of Tokyo, Japan
6 Nippon Meteor Society, Osaka, Japan
7 National Astronomical Observatory of Japan (NAOJ), Tokyo, Japan
Earth's
atmosphere is daily bombarded by billions of dust-sized particles, about 4-200
tonnes of extraterrestrial material per day. Those larger than a few tenths of
a millimetre give rise to visible streaks of light on the night sky called
meteors, or colloquially shooting stars. Meteor science contains many open
questions, and the flux of extraterrestrial material into the Earth's
atmosphere is one of them. It needs to be better quantified.
High-power
MST radars are powerful tools for providing new insights. This talk contains a
review of the analysis algorithms we developed for the 46.5 MHz Shigaraki
Middle and Upper atmosphere (MU) radar in Japan (34.85N, 136.10E), and some
observational highlights. We conducted a systematic set of monthly 24h meteor
head echo observations from 2009 June to 2010 December (>500h) resulting in
more than 100,000 high-quality meteor detections. This data set allows
investigations of meteor characteristics in form of geocentric velocity and
altitude distribution, as well as mapping of the meteor influx seasonal variation.
Meteor
showers are caused by the Earth intersecting streams of meteoroids on orbits
still similar to those of their parent bodies, which are usually comets. Meteor
showers provide opportunities to compare head echo observations with other
observation techniques and simulations. An example of such a comparison is
given: comet1P/Halley dust observed as the Orionid meteor shower. The
comparison indicates that our radar method provides precision and accuracy
comparable to the photographic reduction of much brighter meteors with longer
detectable trajectories.
Presented by: Kero, Johan
Separating
sky and ground wave in indirect phase height measurements
Dieter Keuer , Jörg Trautner
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
Since 1959 indirect phase height
measurements based on continuous ground-based records of long frequency radio
waves reflected in the D-region have been carried out at Kühlungsborn, Northern
Germany. Essentially, the phase height is determined from an analysis of the
local time appearance of minima and maxima of recorded wave amplitudes. This
interference pattern arises because of a superposition of ground and sky wave.
However, the interpretation of this interference pattern in terms of an
ionospheric reflection height relies on the assumption of a constant ground
phase as a phase reference. Obviously, it is of great importance to verify this
assumption. The used transmitter near Allouis (France) is seeded by a caesium normal,
which gives the opportunity to record both amplitude and phase. Using a
GPS-disciplined Rubidium frequency standard and furthermore a second receiving
station 120 km apart from Kühlungsborn a method to separate the sky and ground
wave is presented and corresponding results are discussed.
Presented by: Keuer, Dieter
Boundary layer measurements by the MARA MST radar using a
local bistatic technique.
Sheila Kirkwood , Ingemar Wolf , Daria Mikhaylova
Polar Atmospheric Research, Swedish Institute of Space Physics
The
atmospheric boundary layer (the lowest ~1000 m in the atmosphere) is
partcularly poorly understood and difficult to model in the polar
regions. Strong temperature inversions can build up and the surface
conditions become very dependent on the presence or absence of dynamic mixing
between the surface and the free troposphere. There are several MST radars in
the polar regions which could be used to monitor the boundary layer and provide
valuable input for atmospheric (and climate) modelling, if only they could make
observations at low heights. Generally, the problems of switching between
transmission and reception on the same antenna array limit measurements to
heights above 1000 -2000 m. However, boundary layer measurements down to 400 m
height have been successfully made using small, separate, transmit and receive
arrays (Hocking, 2006). During 2011, MARA (Moveable Atmospheric Radar for
Antarctica) has been augmented with additional receivers and outlier antennas
(for reception only) to make boundary layer measurements at the same time as
the usual monostatic measurements are made throughout the free troposphere, the
lower stratosphere and the mesopause region. Successful technical tests were
made in Kiruna during summer 2011, showing that measurements at least down to
300 m height should be possible. We will report the results of the first full
field tests at the Norwegian Antarctic station Troll, during the 2011/2012
austral summer season.
Presented by: Kirkwood, Sheila
Climatological
characteristics of tropospheric- and lower stratospheric- turbulence over
Kiruna, Sweden
T.
Narayana Rao 1,
Sheila Kirkwood 2
1 National Atmospheric Research Laboratory
2 Swedish Institute of Space Physics
The
measurements made with Esrange Radar (ESRAD) at Kiruna over 15 years have been
used to study climatological characteristics of the turbulence in a
comprehensive way. The turbulence intensity variations are studied as a
function of season, wind direction and wind shear. The turbulence shows
significant seasonal variation in magnitude as well as in height. The
turbulence intensity is quantified in special events like the tropopause folds
and mountain waves. Strongest turbulence at Kiruna is observed in mountain
waves and then in folds. Some of the processes (like tropopause folds)
occurring near the tropopause are reversible and irreversible transfer of
constituents occur mainly due to the turbulence. Also, recently some studies
built climatology of chemical constituents (using air-craft measurements) with
reference to the tropopause. Keeping the above factors in mind, climatology of
the turbulence is studied with the tropopause as a reference altitude. Eddy
diffusivity (K) values are estimated and the seasonal and height
variation of K are compared and contrasted with earlier climatologies of
K. The K values in different seasons are found to be smaller at
Kiruna compared to the reported values elsewhere. Nevertheless, extreme 5‰
values of K are quite large and are comparable with those reported often
in mountain waves and folds. The height variation of K resembles with
that observed in mid-latitudes in some seasons and in tropics in other seasons.
Presented by: Kirkwood, Sheila
PMSE
– a comparison between ESRAD in Arctic Sweden and MARA at Wasa, Antarctica.
Sheila
Kirkwood 1, Evgenia Belova 1, Peter Dalin 1, Maria Mihalikova 1, Daria Mikhaylova 1, Hans Nilsson 1, K. Satheesan 2, Ingemar Wolf 1
1 Polar Atmospheric Research, Swedish Institute of Space Physics
2 Polar Atmospheric Research, Swedish Institute of Space Physics,
now at National Center for Antarctic and Ocean Research, Goa, India
The 52 MHz MST radar ESRAD has been monitoring PMSE at 67° N, 20° E every summer since
1996. MARA (Moveable Atmospheric Radar for Antarctica) operated at the Swedish
summer station Wasa in Antarctica (73° S, 13° W) during four summer seasons
from 2007 to 2011, and will be operated at the Norwegian year-round station
Troll ( 72°S, 2°E) from November 2011. The two radars have been
cross-calibrated in 4 different ways to ensure that PMSE reflectivities can be
properly compared between the two sites. For low levels of geomagnetic avtivity,
PMSE occurrence rates, median reflectivities, and diurnal variations are
similar between the two sites. Modulation by 2-day and 5-day planetary waves is
seen at both sites. At ESRAD (geomagnetic latitude 65° S) there is a strong
dependence of reflectivity on geomagnetic activity, with a relatively high
occurence rate of extremely strong PMSE during disturbed conditions. At Wasa
(geomagnetic latitute 61° S) the response to geomagnetic disturbances is less
extreme, and seems to be delayed by around 1 day. The PMSE height in the early
season is much higher at Wasa than at ESRAD. It is particularly noteable that
the PMSE season over Antarctica starts while the circulation in the
stratosphere is still in its winter (polar vortex) configuration.
Presented by: Kirkwood, Sheila
Objectives
and tasks of the EUMETNET Composite Observing System (EUCOS)
Stefan Klink , Sabine Hafner , Tanja Kleinert , et
al.
EUCOS c/o Deutscher Wetterdienst
EUCOS,
which stands for EUMETNET Composite Observing System, is an EIG EUMETNET
programme whose main objective is a central management of surface based
operational observations on a European-wide scale serving primarily the needs
of regional scale numerical weather prediction (NWP). EUMETNET is a consortium of
currently 29 national meteorological services (NMS) in Europe that provides a
framework for different operational and developmental co-operative programmes
between the services.
The
work content of the EUCOS Programme includes the management of the operational
observing networks, through the E-AMDAR (aircraft observations from commercial
airlines), E-ASAP (radiosonde observations from merchant ships), E-SURFMAR
(buoy and voluntary observing ship measurements) and E-WINPROF (wind profiler)
programmes. Strong links exist to the observation programmes E-GVAP (humidity
measurements derived from global navigational satellite systems data) and OPERA
(‘weather radar’). The coordination of NMSes owned territorial networks (e.g.
radiosonde stations and synoptic stations), data quality monitoring, fault
reporting and recovery, a studies programme for the evolution of the observing
networks and liaison with other organisations like WMO are among the tasks of
the programme.
Changing user requirements on observational data and
external drivers like new developments in measurement technology and observing
systems demand for a periodic redesign of the existing observing networks. Changes in networks should be based
on scientific analyses and therefore EUCOS launched several studies in the
past. Such studies usually comprise of a set of observing system experiments
(OSE) or similar experiments which are run to assess the impact of different
observing systems on NWP forecast skill. NWP groups of NMSes or ECMWF conduct
the studies and EUCOS works as an interface between NWP and data providers.
As an example recommendations derived from a
‘Space-Terrestrial Study’ and an ‘Upper-Air Network Redesign Study’ will be
presented. Another
topic of the presentation will be operational monitoring of EUCOS observation
networks with a special emphasis on E-WINPROF. Finally, an outlook will be
given on future developments in EUCOS, e.g. inclusion of more 3rd
party data, the introduction of a humidity sensor on commercial aircraft within
the E-AMDAR programme or plans for new observing system experiments.
Presented by: Klink, Stefan
The
errors of meteor radar data
Svitlana
V. Kolomiyets
Kharkov National University of Radio electronics (KhNURE)
Errors
of meteor radar data and the problem of hyperbolic meteors are interconnected.
The author used data of the Meteor Automatic Radar System (MARS). MARS was
developed at the Kharkov Institute of Radioelectronics. MARS had high effective
sensitivity (the limiting magnitude for meteors observed was close to + 12 m)
and enabled to carry out an all-round meteor research. Astronomical researches
give synoptically model for geophysical meteor data. Geophysical meteor data
based on meteor drifts measurements. For interpretation of astronomical data it
is necessary to know some results of calculation of errors. The errors of the
Kharkov meteor radar data are resulted. Errors of meteor radar data and the
problem of hyperbolic meteors are discussed.
Presented
by: Kolomiyets, Svitlana V.
Observations
of atmospheric thermal structures during 2009 and 2010 solar eclipses
S.B.Surendra
Prasad 1, M.Venkatarami Reddy 1, A.Hari Krishna 1, K.Krishna Reddy 1, C.J Pan 2, U.V. Murali Krishna 1
1 Yogi Vemana University, Kadapa, India
2 Institute of Space Science, National Central University,Taiwan
Integrated
atmospheric measurements were made at Kadapa, India during the solar eclipses
on 22nd July 2009 and 15th January 2010. Sensitive,
high-resolution meteorological observations revealed dynamical atmospheric
effects despite the presence of cloud. Short-term eclipse related changes
dominated over temperature, wind speed, and wind directions associated with the
synoptic conditions. The solar eclipse is a unique phenomenon gives an
opportunity to investigate the atmospheric effects associated with
comparatively fast solar radiation changes or when incoming solar radiation is
sharply turned off during these events. The temporal variations of the temperature
profiles caused by a solar eclipse at about a fixed point aloft are studied by
using radiosonde sounding with 3-hour interval resolution, Mini Boundary Layer
Mast (MBLM) and COSMIC GPS RO data for 15 January 2010 whereas for 22 July 2009
magnetometer data is additional collected. It is the first time to observe the
whole evolution of cooling and heating processes within solar eclipse period.
As the approaching the maximum, a very efficient cooling process from surface
to about 40 km altitude are noticed. The temperature decreases in stratosphere
are much more than those decreases in the troposphere. On the other hand,
significant warming takes place at stratosphere in 3 hours after the maximum
eclipse is also noticed. Wave-like temperature variations with vertical
wavelength about 3-5 km occurred at 11:30 IST as the maximum eclipse taking
place. As the inversion layers are not frequently reported in the lower
stratosphere and they only last about few hours in this study, these wave-like
structures may be due to the Gravity wave induced by the solar eclipse that
deserves more study. As the too short life time observes here, it seems reply
why there is rare report of those wave activities related to solar eclipse.
From COSMIC GPS RO a significant cooling is observed during the 15 January 2010
solar eclipse in lower stratosphere where as 22 July 2009 is dominant warming
is observed in lower stratosphere compared to the non eclipse days. Details of
the thermal perturbation noticed during annular solar eclipse and total solar
eclipse to be discussed.
Presented by: Krishna, U.V.
Murali
Investigations
on Tropospheric ducts by using wind profiler radar and Artificial Neural
Network over PALAU in the Pacific Ocean
Punyaseshudu
Dupadu 1, Madhusudhana Kallu 2, K.Krishna Reddy 3, U.V. Murali Krishna 3
1 Rayalaseema University, Kurnool – 518 002, India
2 Sri Krishnadevaraya University, Anantapur-515002, India
3 Yogi Vemana University, Kadapa – 516 003, Inida
A
detailed description of ducts (A rapid change in air temperature and humidity
with height leads to the generation of tropospheric ducts) and their relevance
to radiowave propagation over the Pacific Ocean in the Island of Palau using
ground-based wind profiler radar, Radiometer and Radiosonde has been presented.
The constantly changing weather conditions over the Ocean mean that marine and
coastal environments, in particular, are prone to these unusual tropospheric
phenomena that facilitate radio waves to have higher signal strengths and to
travel longer distances than expected. Therefore, the influence of evaporation
ducts on over-sea radiowave propagation needs to be thoroughly investigated. In
this work, an artificial neural network (ANN) model is developed and used to
predict the presence of ducting phenomena for a specific time, taking into
account ground values of atmospheric pressure, relative humidity and
temperature. A feed forward back propagation ANN is implemented, which is
trained, validated and tested using atmospheric radiosonde data from the Koror,
for the period from 2004 to 2007. The data analyses showed that the wind
profiler is able to detect ducting conditions through (i) strong correlation of
increase in the turbulence structure function parameter, Cn2, with
negative values of dM/dz and (ii) agreement in increase in potential refractive
index (estimated from radar data) with increase in potential refractive index
obtained from radiosonde data, within the duct region.
Presented by: Krishna, U.V.
Murali
Accurate
track prediction of cyclones over bay of Bengal using
WRF model
M.Venkatarami
Reddy , S. Balaji Kumar , S.B. Surendra Prasad , K.Krishna Reddy , U.V.
Murali Krishna
Yogi Vemana University, Kadapa, India
Tropical
cyclones that form over the Bay of Bengal and Arabian Sea during pre-monsoon
(April-May), early monsoon (June), late and post monsoon (September-November)
cause vulnerable damage to lives and property over the coastal regions of India
with strong winds, heavy rain and tidal wave. The numerical models based on
fundamental dynamics and well-defined physical processes provide a useful tool
for understanding and predicting Tropical Cyclones (TC). For accurate forecast
of TC, it is essential that numerical models must incorporate realistic representation
of important physical and dynamical processes as they play crucial role in
determining genesis, intensification and movement. In the present study,
numerical simulation experiments on severe cyclone Storm “LAILA” (17-21
May, 2010) and "JAL” (04-08 November, 2010)is
performed. For “LAILA” and “JAL” track prediction, a fully
compressible, non-hydrostatic Advanced Research Weather Research and
Forecasting (ARW-WRF) model with Arakawa C-grid is utilized. The advanced
research WRF model was run at grid spacing of 27 km, 9 km and 3 km. The cyclone
track study is done with National Center for environmental prediction (NCEP),
final analysis fields (NCEP FNL) or the reanalysis data with 1.0 x 1.0 degree
grid resolution used as initial and lateral boundary conditions for the WRF
model. In JAL cyclone track prediction, WRF modeling was performed by
changing cumulus schemes such as Kain Fritsch (KF), Betts-Miller-Janjic (BMJ),
Grell-Devenyi (GD) and New Grell (NG) without changing microphysical
properties, PBL, Radiation Schemes and Dynamics. The track
observed with Kain Fritsch (KF) scheme is well compared temporally and
spatially with Indian Meteorological Department (IMD) observed track and the
remaining Betts-Miller-Janjic (BMJ), Grell-Devenyi (GD) and New Grell (NG)
schemes too suitable with IMD observed track only spatially. The cyclone centre
pressures, maximum cyclone surface wind speed obtained from the model are well
compared with the IMD data. The variation of pressure, temperature and humidity
parameters from the Automatic Weather Station at Yogi Vemana University, kadapa
(14.47°N; 78.82°E) a semi arid region,SHAR-sulurupet
(13.690N, 80.220E) and Indhukurpet(14.460N,
80.080E) coastal area of India, during the cyclone landfall was
analyzed and compared with the modeled parameters. Also we compared the
Reflectivity and Doppler Velocity for both cyclonic and non-Cyclonic day using
Chennai Doppler Weather Radar. The results are in reasonable in
good agreement.
Presented by: Krishna, U.V.
Murali
Ground-Based
Wind Profiler Radar and Lidar Measurements of Marine Boundary Layer evolution
over PALAU in Pacific Ocean
U.V.Murali
Krishna 1, K.Krishna Reddy 1, R Shirooka 2
1 Yogi Vemana University, Kadapa,India
2 Japan Agency for Marine-Earth Science and Technology, Yokosuka,
Japan
We
carried out research at Palau Islands focusing on the Pacific Area
Long-term Atmospheric observation for Understanding of
climate change (PALAU)projecttounderstand the
mechanism of cloud-precipitation processes, land-atmosphere and air-sea
interactions over the warm water pool, focusing on seasonal and intra-seasonal
variations. We installed several ground based remote sensors at Peleliu and
Aimeliik experimental sites in the Palau. For the present study, Wind Profiler
Radar (WPR) and Disdrometer are utilized for preliminary understanding of the
marine boundary layer (MBL) evolution, diurnal and seasonal variation of
precipitating cloud systems associated with easterly and westerly monsoon. To
check the WPR performance, a comparison study with Korror radiosonde data is
carried out. The results show fairly good agreement between the two
measurements considering the spatial separation and data acquisition. The
analysis showed that Ventilation Coefficient (VC) is strongly influenced by
wind speed during westerly and easterly monsoon; whereas both MBL height and
wind speed determine the value of VC during the other seasons over Palau.
Ceilometer is a robust instrument that provides continuous and accurate
cloud-base determinations as a standard output. Combined information of
ceilometer aerosol backscatter data with the WPR, MRR and JWD allows us to
investigate how the radiative effects of aerosol correspond to changing
meteorological events (easterly and westerly or/during inactive and active
phase of MJO) and regional regimes. Also investigated the
characteristic features of cloud base height (CBH) over Aimeliik during
different seasons (easterly & westerly monsoon). The CBH shows
distinct diurnal and seasonal variations during all the seasons and found a
minimum during the westerly wind monsoon regime.
Presented by: Krishna, U.V.Murali
Observations
and modeling studes on severe thunderstorms over north east region of India
S.Balaji Kumar , U.V.Murali Krishna , M.Venkatarami Reddy ,
K.Krishna Reddy
Yogi Vemana University, Kadapa, India
Thunderstorm
is a mesoscale system with space scale of a few kilometers to a couple of 100
kilometers and time scale of less than an hour to several hours characterized
by heavy rain showers, lightning, thunder, hail-storms, dust-storms, surface
wind squalls, down bursts and tornadoes. Thus, the severe thunderstorms have
significant socioeconomic effects in the lives of people of the region. In
India, during the pre-monsoon season of April and May, North –Eastern region of
India is affected by severe thunderstorms called ‘Norwesters’ that are locally
called Kal Baishaki. It is thus important to understand the growth and decay
process and prediction of these severe local storms. A national coordinated
intensive observations are conducted over Guwahati (26o 17’ N, 91o
77’ E), NER of India since 2006 to study the physical and thermo dynamical
characteristics of thunderstorms and also forecasting. Since 2009 onwards we
carried out field experiments by deploying Micro Rain Radar and PARSIVEL
(Particle size and Velocity) Disdrometer. Apart from these we have collected
India Meteorological Department (IMD) surface sensors (a network of current
weather system, GPS, meteorological sensors, X-band Radar and Radiosonde) data.
During 2010 year STORM field campaign, 32- precipitating cloud systems are
captured with 22 thunderstorm days (TS) , 4 hail storm days (HS)and 6 non
thunderstorm days (NTS) with a total rain accumulation of 6123 mm. Nine Squall
lines passed over Guwahati with maximum number of squall in the month of April.
The significant difference observed between the drop size distributions at the
beginning of the thunderstorm and those found later in the storm for equal
rainfall rates has been attributed to the difference in the terminal velocities
of the small. Such variations in drop size distribution were not observed for
the non-thunderstorm rainfall. Apart from these, we also noticed coexisting
rain and hail particles that are distinguishable based on their size, fall
velocity. Rainfall intensity is greater in TS days compared to NTS days.
Maximum rainfall in TS day is 119.3 mm on 2nd may 2010 and for NTS
day is 10.0 mm on 19th May, 2010. Micro rain radar (MRR) vertical
profile of Drop size distribution show the existence of maximum occurrence of
convective clouds during TS whereas mixed and stratiform clouds observed during
TS precipitating event. Radar Reflectivity(Z) – Rain
Rate (R) relations obtained from Disdrometer and MRR clearly distinguished the
TS and NTS days. An attempt has been made in the present study to simulate a
thunderstorm event that occurred on 22nd, 24th April and
13th May 2010 at Guwahati (26.106o N, 91.585o
E) using the Fifth-Generation PSU/NCAR Mesoscale Model (MM5) and Weather
Research Forecasting (WRF) model .
Presented by: Krishna, U.V.Murali
Overview
of VHF radar observations of equatorial mesosphere and ionosphere
Erhan
Kudeki 1, Gerald Lehmacher 2, Pablo Reyes 1, Marco Milla 3, Jorge Chau 3, Karim Kuyeng 3, Levent Gezer 1
1 University of Illinois at Urbana Champaign, USA
2 Clemson University, South Carolina, USA
3 Jicamarca Radio Observatory, Lima, Peru
Equatorial
ionosphere provides a nearly uninterrupted distribution of VHF radar targets
during daytime hours over the altitude range of 50 to several hundred
kilometers. These targets can act as tracers of atmospheric wave motions and/or
wind driven dynamo fields which develop in the region. Below 90 km we have
mesospheric backscatter (“M” of the “MST” radar response) from Bragg scale
electron density irregularities produced by mesospheric turbulence and mixing
processes exhibiting a height dependent aspect sensitivity and correlation
times. Backscatter from the equatorial E-region is dominated by plasma
turbulence associated with the gradient-drift and two-stream plasma instabilities.
The region extending from ~135 to 180 km exhibits the so-called 150-km echoes
of unknown origin. While the physics of 150-km echoes is not understood, the
spatial and temporal signatures of scattered radar echoes from the region
strongly indicate that interactions and processes involving gravity waves must
be playing a major role in this phenomenon. Finally, the quiescent daytime
ionosphere above the 150-km region, namely the F-region ionosphere, is
observable (at least in principle) in the incoherent scatter mode by VHF radars
with sufficient power-aperture product for daytime observation of the
mesosphere in the MST mode.
The
50 MHz Jicamarca radar located near Lima, Peru, has the MST and incoherent
scatter radar (ISR) capabilities outlined above. During the past decade
multi-beam joint MST/ISR observations modes have been developed at Jicamarca
given a number of advantages associated with such operations. In MST wind
measurements multi-beam radar operations are essential. Since magnetic aspect angles
vary across the individual MST beams, the weak incoherent scatter returns
detected by these beams from F-region altitudes exhibit a
diversity in magneto-ionic polarization response and enable F-region
electron density (Ne) estimation. Since ISR backscatter
cross-sections are known functions of Ne in probed regions, density
estimation calibrates the radar for ISR as well as MST measurements. It is
becoming increasingly attractive to use the described joint MST/ISR mode in
long-term (several days) Jicamarca campaigns of either mesospheric or
ionospheric focus since its additive costs are marginal and its potential
benefits are substantial in case of unpredictable events such as solar flares,
magnetic storms, and sudden stratospheric warming events. Examples of joint
MST/ISR data collected during such events will be presented.
Presented by: Kudeki, Erhan
VHF
radar observations of non-linear interactions of convectively generated gravity
waves using bispectral approach
Kishore
Karanam Kumar
, Kizhathur Narasimhan Uma , S.R. John
Space Physics Laboratory, Vikram Sarabhai Space Centre,
Thiruvananthapuram-695022, India.
Cumulus
convection has received a great deal of attention as a possible source of
gravity waves. Now, it is well established that apart from contributing to the
drag in the middle atmosphere, convectively generated gravity waves (CGWs)
modify the region around the clouds. The exact parameterization of these
convectively generated gravity waves needs thorough understanding of such waves
including their source mechanisms. In this regard, the present study attempts
to discuss the non-linear interactions of convectively generated gravity waves.
Continuous VHF radar observations with high temporal resolution of mesoscale
convective systems (MCS) are made use for the preset study. The vertical
velocity estimates within the MCS form the basis of the analysis. The wavelet
spectra of vertical velocity have shown the signature of CGWs in the upper
troposphere and lower stratosphere. To study the non-liner interaction among
the various harmonics of CGWs, the bispectrum is estimated. The bispectrum
analysis using higher order statistics showed the non-liner interaction among
the harmonics of CGWs, which is noteworthy result from the present analysis.
The results depicted here will have important implications in explaining the
observed period of CGW in the middle atmosphere.
Presented by: Kumar, Kishore
Karanam
New
insights into the ambipolar diffusion of meteor trails
Kishore
Karanam Kumar
1, K.V. Subrahmanyam
1 Space Physics Laboratory, Vikram Sarabhai Space Centre,
Thiruvananthapuram-695022, India
Radar
echoes from underdense meteor trails have been used to infer the temperature in
the 80-100 km region of the atmosphere for decades. Different methods have been
used to derive mesospheric temperature values from the meteor decay times and
themethod of retrieving temperature has gone through several modifications
since its inception.The direct measurements of the ambipolar diffusion
coefficient and then conversion to a temperature using assumed values of the
pressure is a standard method to retrieve the temperature profile. However, the
important assumption in all these methods is the ambipolar diffusion of the
meteor trail. So far there are no independent measurements of ambipolar
diffusion coefficient to validate this assumption in the height region of
80-100 km. In this regard, we have estimated height profile of ambipolar
diffusion coefficient and hence the decay time using temperature and pressure
measurements by SABER, which is independent of radar measurements. The
comparison of the meteor trail decay time measured by meteor radar at Thumba
(8.50 N, 770 E), and SABER provided very valuable
insights into the meteor decay times and also provided much needed validation
for assumption of ambipolar diffusion of meteor trail. It is observed that the
assumption of ambipolar diffusion is valid only in the height region of 92-100
km where both SABER and radar measurement show excellent agreement in decay
times. The present analysis also shows that there are other processes which
govern the meteor decay in the 80-90 km region. The difference between the
SABER and radar observed decay times are estimated and it is observed that it has
very small day-to-day variability. However, there is pronounced diurnal
variation in the difference profile. The diurnal variation of difference
profile of decay times are quantified for each season and this correction is
applied for temperature retrieval, which showed considerable improvement. The
important outcome of the present study is the validation of assumption on
ambipolar diffusivity of the meteor trails.
Presented by: Kumar, Kishore
Karanam
Simultaneous
observations of small-scale structures in Mesosphere Lower Thermosphere winds
and temperature using Meteor radar and OH day-glow photometer over Thumba (8.50
N, 770 E)
Kishore
Karanam Kumar
, K.V. Subrahmanyam , C. Vineeth , T.K. Pant
Space Physics Laboratory, Vikram Sarabhai Space Centre,
Thiruvananthapuram-695022, India
Simultaneous
observations of gravity wave induced small-scale structure in the winds and
temperature were carried out for the first time over a low-latitude station
Thumba. The radial velocities measured within the meteor radar volume are
segregated in terms of height, zenith and azimuth angles for further analysis.
Two dimensional Fourier analysis is carried out to quantify both the observed
time period as well as horizontal wavelength. During the meter radar
observations a co-located OH day-glow photometer was operated in the scanning
mode at a fixed azimuth angle. . The OH emissions carry signatures of the
gravity waves, tidal forcing and planetary wave phenomena which greatly
influence the mesosphere lower thermosphere (MLT) processes. As the OH emission
layer is located at around 87 km with a thickness of about 9 km, it is believed
that the temperature measured by the day-glow photometer represents the
atmospheric temperature around 85 to 90 km. This height region is thus overlaps
with the meter radar measurements. However, with respect to the temperature
measurements it must be remembered that the temperature measured is a weighted
average over the emission layer. Thus we obtained simultaneous observations of
wind and temperature structures within the MLT region. After quantifying the
spatial and temporal variability of wind and temperature, an attempt is made to
study the spatial variability of ambipolar diffusion within the radar volume
and the same is discussed in the light of day-glow photometer observed
temperature structure. It is envisaged that the present study will have
important implications in understanding the small-scale spatial variability
observed in the MLT region.
Presented by: Kumar, Kishore
Karanam
Variation
of turbulence intensity in cirrus clouds
S.
Satheesh Kumar ,
T. Narayana Rao
National Atmospheric Research Laboratory
It
is widely accepted that the exchange between the troposphere and stratosphere
in tropics occurs primarily through two mechanisms: a fast transport by
convection or a slow transport by stratospheric diabatic circulation. Among
these processes, the role of convection in dehydrating the air entering into
the stratosphere from troposphere is highly debated. Nevertheless, there is a
consensus that the turbulence transport in overshooting convective cores is one
of the important stratosphere-troposphere exchange mechanisms. Recent studies
at Gadanki noted a clear enhancement in turbulence activity in draft cores with
the magnitude of turbulence intensity nearly 4.5 times larger in convective
cores than in fair weather. Also, recent air craft measurements have reported
moderate-marginally severe turbulence not only in active convection regions but
also far away from active convection in the anvils. The present study,
therefore, attempts to quantify the turbulence intensity in anvil clouds by
combining MST radar and Lidar measurements made over Gadanki during 1998-2011.
About 650 coincident data sets were collected to study the variability of the
turbulence in anvil clouds.
Presented by: Kumar, S. Satheesh
MAARSY
- The new MST radar on Andøya: system description and first results
Ralph
Latteck , Werner
Singer , Markus Rapp , Toralf Renkwitz , Gunter Stober , Marius Zecha
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
The
Middle Atmosphere Alomar Radar System (MAARSY) on the North-Norwegian island Andøya is a 53.5MHz monostatic radar with an active
phased array antenna consisting of 433 Yagi antennas. The 3-element Yagi
antennas are arranged in an equilateral triangular grid forming a circular
aperture of approximately 6300m2. Each individual antenna is
connected to its own transceiver with independent phase control and a scalable
power output of up to 2 kW. This arrangement provides very high flexibility of
beam forming and beam steering with a symmetric radar beam of a minimum beam
width of 3.6°. The system allows classical beam swinging operation as well as
experiments with simultaneous multiple beams and the use of interferometric
applications for improved studies of the Arctic atmosphere from the troposphere
up to the lower thermosphere with high spatio-temporal resolution. The
construction of MAARSY started in May 2009 and has been completed in May 2011.
Besides standard observations of tropospheric winds and polar mesosphere summer
echoes, the first multi-beam experiments using up to 97 quasi-simultaneous
beams in the mesosphere have been carried out in 2010 and 2011. These results
provide a first insight into the horizontal variability of polar mesosphere
summer and winter echoes with time resolutions between 3 and 9 minutes. In
addition, first meteor head echo observations were conducted during the Geminid
meteor shower in December 2010.
Presented by: Latteck, Ralph
Quantifying Atmospheric Turbulence: A validation of the
spectral width method with MST radar, boundary layer wind profiler, and
aircraft measurements.
Christopher
Lee
Centre for Atmospheric Science, University of Manchester
Quantification
of turbulence with wind profiling radars has been investigated for decades. The
methods used have been continually refined, becoming increasingly complex with
fresh mathematical insight, but even the most basic approaches have barely been
tested against in-situ measurements. This investigation tests the spectral
width method, using a MST radar, a boundary layer wind
profiler, and many hours of in-situ aircraft observations. The results
highlight the gulf between the theoretical and practical application of radar
quantification methods.
There
has been a pressing need for a comparison of this nature. Comprehensive
climatologies of atmospheric turbulence are needed to support the continuing
drive towards weather models with finer resolutions.
Turbulence
can be measured using the width of a radar’s Doppler velocity spectrum; in
stronger turbulence there is a greater spread of turbulent velocities, and so a
broader Doppler spectrum width. Alongside turbulence, other factors can broaden
the spectrum, and the crux of the spectral width method is to remove those
non-turbulent contributions. The most prominent is Beam Broadening, which
occurs because the radar observes turbulence over a large volume of the
atmosphere. Initial proposals for its correction were straightforward, but more
recent studies have combined its correction with other contributions, such
Shear Broadening. This study has shown that, whilst the more complex ‘combined
broadening’ form of correction is mathematically rigorous, the technical
limitations of a radar can make such improvements insignificant; indeed, under
some conditions the simpler approach, which considers broadening terms
separately, is more accurate.
Accuracy
aside, how representative are radar measurements of turbulence? Aircraft-radar
comparisons over the complex terrain surrounding the Capel Dewi MST radar site,
in West Wales, show that the variability in spectral widths can be used to
quantify fluctuations in turbulence strength over wide areas.
The
results presented in this talk provide an extensive validation of the spectral
width method, alongside the limitations of the technique. The comparison with
in-situ measurements has shown that, with the correct approach, wind profiling
radar can be used to quantify atmospheric turbulence in the radars
surroundings, paving the way to the first comprehensive climatologies of
turbulence in the troposphere and stratosphere.
Presented by: Lee, Christopher
Conjuring a Gaussian: A new signal processing approach for
turbulent Doppler spectra.
Christopher
Lee
Centre for Atmospheric Science, University of Manchester
Doppler
radar wind profilers present the best opportunity to construct comprehensive
climatologies of atmospheric turbulence. The spectral width method holds the
greatest promise, but above the boundary layer, where turbulence is often
‘patchy’, its key assumption often breaks down: The spectral width method
assumes that turbulent Doppler spectra have Gaussian shapes, but in the free
troposphere that condition is rarely met. To overcome that problem, this study
presents a new approach to Doppler spectrum quantification, constructing
Gaussian spectra from non-Gaussian measurements of patchy turbulence.
Many
studies have encountered difficulties when quantifying sparse turbulence: The
spectral width method assumes that turbulence fills the radar observation
volume, so that the ensemble of motions can be measured. Where observation
times are too short spectra are non-Gaussian, introducing errors into the
quantification of turbulence. Averaging consecutive spectral widths, and the fitting
of Gaussians, have both been used to reduce those errors, but neither method is
ideal. This study presents a reliable alternative: Combining consecutive
Doppler spectra effectively increases the observation time of the radar, and
creates a Gaussian spectrum, from which turbulence can be quantified.
Obtaining
a Gaussian spectrum is only part of the problem; non-turbulent signals, such as
specular reflections, ground clutter, and other contaminants, can make spectral
width quantification difficult. This study shows that existing atmospheric
signal identification routines used with wind profiling radars (usually
tailored for the recovery of winds) can be combined with Gaussian fitting of
the Doppler spectrum, and spectral combination, to dramatically improve the
accuracy of spectral width retrieval.
Applicable
to both boundary layer wind profiler and MST radars, the results presented in
this poster demonstrate that the new treatment of Doppler spectra can be used
to dramatically increase the accuracy of wind profiler turbulence
quantification.
Presented by: Lee, Christopher
Development
of 53 MHz Multi-Mode Radar for Atmospheric Probing
Parvatala
Srinivasulu 1,
Polisetti Yasodha 1,
P. Kamaraj 1,
Meka Durga Rao 1,
S. Narayana Reddy 2,
A. Jayaraman, PP Leena 4
1 National Atmospheric Research Laboratory, Gadanki – 517 112, India
2 S V U College of Engineering, S V U Campus, Tirupati – 517 502
4 National Atmospheric Research Laboratory, Department of
Space,Government of India
Indian
MST radar, evolved under the middle atmosphere program (MAP), is a valuable
atmospheric remote sensing tool. It is planned to upgrade this radar, which is
operating since 1992, to an active array system using high power solid-state
transmit-receive (TR) modules. A separate 133-element pilot array, external to
the existing MST radar array, is installed to verify the design concepts like
out-door installation of TR modules, Optical Ethernet-working, multi-channel
direct digital processing, pulse-to-pulse beam switching, automatic phase
calibration etc. All subsystems have been developed and installed except the TR
modules, which are being integrated into the system in a phased manner. At
present the system is being operated in Doppler beam swinging (DBS) mode with
partial array filling. The measured winds are validated by comparing them with
those derived from a collocated GPS Sonde.
The
quasi-circular shaped antenna array comprises 133 three-element Yagi elements
arranged in 7 hexagonal segments, each consisting of 19 elements with
triangular grid spacing of 0.7l. Each element of the array is fed directly by a
dedicated and collocated 1kW solid-state TR module, which consists of a MOSFET
high power Amplifier and low noise receive section connected
to a common antenna port through a high-power passive transmit/receive (T/R)
switch. An input section, containing a digital phase shifter and digital
attenuator, is switched between transmit and receive paths by means of a
low power T/R switch. A timing and control signal generator (TCSG) card inside
the TR module generates the timing and control signals with reference to the
input trigger pulse. TCSG is interfaced with optical Ethernet for remote
operation. The out-door TR modules are connected to the in-door radar instrumentation
through six-core optical fiber cable and Ethernet switches. Media
converters are used on either side of the optical fibers to convert the trigger
pulse, reference clock, Tx cal and Rx cal signals from
electrical to optical and vice versa.
The
DDS-based radar exciter signal is distributed and fed to the 133 TR modules.
The receive signals are combined in the respective antenna segments and
delivered to the multi-channel direct digital receiver via seven-channel
back-end RF unit. A PC-based radar controller (RC) controls the TR modules
through optical Ethernet interface network. Multiple GUI is designed for
setting the subsystems, calibration and operation of the system. At present,
the central antenna segment has been activated with the TR modules and
validated with DBS operation while the TR modules are being installed for the
rest of the array.
This
system is designed for multiple modes of operation such as DBS, Spaced antenna,
interferometry, FDI, IDI etc.
Presented by: Leena, PP
Development
and Validation of L-band Active Array Lower Atmospheric Radar Wind Profilers at
NARL
Parvatala
Srinivasulu 1,
Polisetti Yasodha 1,
P. Kamaraj 1,
T. Narayana Rao 1,
S. Narayana Reddy 2,
A. Jayaraman 1,
PP Leena 3
1 National Atmospheric Research Laboratory, Gadanki – 517 112, India
2 S V U College of Engineering, S V U Campus, Tirupati – 517 502
3 National Atmospheric Research Laboratory, Department of
Space,Government of India
NARL
has developed new 1280 MHz radar wind profiler for lower atmospheric research
applications. This system, configured with active array and a passive
two-dimensionalmodified Butler beam forming network, operates in Doppler
beam swinging mode. It also has advanced features like direct IF digital
processing and pulse compression schemes. Two profilers have been
built and successfully validated.
Low
cost dedicated solid-state 10W transceiver modules, realized with
commercial communication components, are used to feed the individual microstrip
patch antenna elements of the square array. Each transceiver consists of a
power amplifier (PA) and low noise amplifier (LNA) connected to the common
antenna port through a circulator. A transmit/receive switch switches the input
port between the PA and LNA. The low power two-dimensional beam-forming
network, realized on a printed circuit board, distributes the exciter output
signal and feeds the transceivers with appropriate amplitude and phase distribution
to generate different beams. This configuration, which is a simplified active
array, eliminates the antenna feed loss and achieves best signal-to-noise
ratio, thereby increased range coverage. Consequently, this scheme allows
smaller antenna size when compared to a conventional passive array system, for
the given range performance, and makes the wind profiler compact and
transportable. Beam switching is done by controlling a solid state
single-pole-multi-through switch. Main advantage of the passive beam forming
network is that it avoids the need for periodic phase calibration. Pulse
compression feature enhances the height coverage without affecting the range
resolution. Direct IF digital processing has advantages like better dynamic
range, flexibility, programmability etc,.
Two
wind profilers, of 1.4m and 2.8m size each, have been developed. The smaller
wind profiler, with an 8x8 array and 64 transceivers, is built as pilot radar
to validate the design concepts. It has been deployed at three locations since
May 2010 and yielded excellent wind and precipitation data. The larger wind
profiler, built with 16x16 array and 256 transceivers, is a stationary system
located inside a room for which the planar array acts as roof. This profiler is
operating at NARL since March 2011. Typical height coverage (max height) of
this system is 4-7 km for the clear air case and 6-14 km during precipitation.
Both profilers have been validated by comparing the winds with those obtained
by a collocated GPS Sonde.
Presented by: Leena, PP
Characteristics
of high frequency gravity waves observed using simultaneous high resolution
radiosonde and MST radar observations
PP Leena 1, M. Venkat Ratnam 1, B.V. Krishna Murthy 2
1 National Atmospheric Research Laboratory (NARL)
2 B1, CEEBROS, Chennai
The
subject of gravity waves (GWs) has occupied a crucial role in the current
atmospheric research due to their myriad effects on atmospheric structure and
dynamics. It is well known that GWs play a major role in transporting energy and
momentum, in contributing to turbulence and in mixing and influencing the mean
circulation and thermal structure of the middle atmosphere. Studies have shown
that parameterization of gravity wave drag is required in large-scale numerical
models for realistic simulations of the middle atmospheric circulation. For
this parameterization, parameters related to wave characteristics are needed
which can be determined from observations. Climatology of GWs including
complete spectrum is a vital aspect in understanding their role in atmospheric
phenomena.
Radiosonde
data are widely used for GW research due to their extensive geographical
coverage. Until now most of the GWs characteristics reported using radiosonde
observations are of low frequency waves. In the present study characteristics
of high frequency GWs has been studied by using simultaneous high resolution
radiosonde and MST radar using five years of data (2006-2011) collected from
Gadanki (13.5oN, 79.2oE). Analysis has been done
separately for troposphere (1-16 km) and lower stratosphere (16-28 km) and
found that these GWs have the vertical (horizontal) wavelengths of 6-12 km
(100-300 km) and 3-7 km (100-500 km) in the troposphere and lower
stratospheres, respectively. These characteristics are completely different
with that reported for inertial periods for Gadanki station. Most striking
result obtained using simultaneous radar observations is that these GWs have
periods of 2-6 hours. Horizontal direction of propagation shows that they
propagate towards south-east/north-west irrespective of seasons. But in the
stratosphere they propagate towards south east direction in the monsoon season.
These
studies have been further extended for the radiosonde stations of Truk,
Rochambeau, Singapore, Seychelles and Darwin distributed across the globe
within ±15olatitude and extracted high frequency GW components. This
study, if implemented across the globe, will help to parameterize the high
frequency GWs also in the global models.
Presented by: Leena, PP
The
challenge of providing continuous high-quality measurements with an operational
radar wind profiler network
Ronny Leinweber , Volker Lehmann
German Meteorological Service (DWD) , Lindenberg Meteorological Observatory /
Richard-Aßmann-Observatory, 15848 Tauche OT Lindenberg, Germany
Ground
based remote sensing of the vertical profile of the horizontal wind by radar
wind profiler (RWP) has been significantly developed since the first
demonstration of clear air radar measurements in the early 1970s and there exist
several operational networks of RWP worldwide. One example is the CWINDE
network in Europe, which is currently comprised of 30 profilers. Many of the
CWINDE RWP provide high quality wind measurements in
real-time and it is only such data that can be successfully assimilated in
numerical weather prediction models. The main challenge of running such
networks is therefore to continuously provide high quality data in a
sustainable fashion on a 24/7 basis. It is well known that RWP are able to
provide high-quality measurements if they are well-operated and
well-maintained. However, these seemingly trivial requirements require a
constant endeavor in the operational practice.
The Deutscher Wetterdienst is operating an operational wind profiler network
since 2003. It consists of four 482 MHz RWP which are also part of the CWINDE
network. Based on our experience in CWINDE, the presentation will focus on
practical aspects and problems which are most relevant for the operational use:
Frequency management, proper system configuration (in particular signal
processing and quality control), maintenance and data monitoring.
The high sensitivity of the RWP makes them vulnerable to any external
radio-frequency interference (RFI) of sufficient strength that is in band. As
more and more technical applications are using electromagnetic waves, frequency
spectrum has become a scare resource. Effective frequency management is
therefore an essential issue for operational networks. Nevertheless, RFI is an
increasing problem and needs to be considered to avoid spurious data.
Clutter and its detection and filtering is a
longstanding problem of RWP. Signal processing and quality control needs to be
constantly refined to guarantee a high level of data quality, even with new
clutter types like wind turbine echoes. Modern RWP software packages make it
possible to address particular clutter problems through a customized
processing. This can be very helpful for the suppression of site specific
clutter or RFI.
RWP
are complex instruments and regular maintenance is necessary to guarantee high
level of data quality. This includes both hardware and software. As an example,
the advantages of a system upgrade for the DWD RWP network in 2011 will be
presented.
Most important for any operational system is a continuous data quality
evaluation which is nowadays mainly based on statistical comparison with
state-of-the-art NWP models. An example of the capabilities of NWP monitoring
to identify a hardware issue with a 482 MHz profiler will be presented.
Presented by: Lehmann, Volker
Comparison
of wind profiler radar measurements with Doppler Wind Lidar profiles
measurements at the Lindenberg GRUAN site
Ronny
Leinweber 1, Stefan Emeis 2, Bernd Stiller 1, Simone Lolli 3, Matthias Mauder 2, Ludovic Thobois 3, Volker Lehmann 1
1 German Meteorological Service (DWD) , Lindenberg Meteorological
Observatory / Richard-Aßmann-Observatory, 15848 Tauche OT Lindenberg, Germany
2 IKT- Institute of Meteorology and Climate Research (IMK-IFU)
Kreuzeckbahnstraße 19 82467 Garmisch-Partenkirchen, Germany
3 LEOSPHERE, 76 Rue Monceau, 75008 Paris, France
The
wind field is one of the most important atmospheric parameters. Its accurate
measurement with a high spatial and temporal resolution is crucial for the
improvement of Numerical Weather Prediction (NWP) models as well as necessary
to obtain reliable calculations of transport of air pollution and trace gases.
Radar wind profilers (RWP) are the most thoroughly developed and widely used
sensors for ground based remote sensing of the wind field. They provide
vertical profiles (up to 15 km) of the horizontal wind at high temporal
resolution under all weather conditions, that is in
both the cloudy and clear atmosphere. Moreover, new portable wind Doppler lidar
systems have been developed due to requirements of the rapid growing wind
engineering to measure the wind field. Since these systems work in the near
infrared spectrum (1.4 µm – 2.2 µm) the vertical range of the measurements
depend on both clouds and aerosol content. These very compact systems
complement the group of remote wind field sensors.
We present a comparison of two different Doppler Wind Lidar systems, developed
by Leosphere and Halo Photonics, respectively, with a 482 Mhz
Wind Profiler. The comparison was done at the Lindenberg GCOS Reference
Upper-Air Network (GRUAN) site for a period of two months (October/November
2011). Radiosonde and NWP model output data was additionally used for the
comparison.
The 482 MHz radar wind profiler was operated in a 4-beam Doppler Beam Swinging
(DBS) configuration similar to Leosphere lidar. The Halo lidar was configured
to use a classical Velocity Azimuth Display (VAD) configuration using 24
discrete beams. The paper will present the first results of this
intercomparison.
Presented by: Leinweber, Ronny
PMSE
observations with the EISCAT VHF and UHF-radars: Ice particles and their effect
on ambient electron densities
Qiang Li , Markus Rapp
Leibniz-Institute of Atmospheric Physics
(IAP) at the Rostock University, Kühlungsborn, Germany
Polar
mesosphere in summer is host to the coldest temperature on Earth leading to the
presence of nanometer-size ice particles which can become charged due to
electron attachment. This process modifies the charge balance in the ambient
environment. It is now common belief that polar mesosphere summer echoes (PMSE)
originate from turbulence induced scatter in combination with a large Schmidt
number due to the presence of charged ice particles. According to this theory,
volume reflectivity-ratios of PMSE simultaneously observed at two frequencies
can be used to calculate the Schmidt number and hence radii of the charged
aerosol particles. In this study, we do this exercise on the simultaneous PMSE
observations with the EISCAT VHF and UHF radars, collocated near Tromso (69oN,
19oE) and operated at frequencies of 224 and 930 MHz, respectively.
The resulting particle radii both display excellent agreement with expectations
from microphysical models and independent optical observations of microphysical
ice parameters. Furthermore, electron densities deduced from the
UHF-observations (i.e., in the absence of UHF-PMSE) have been used to
statistically study electron density depletion in the presence of PMSE
simultaneously observed with the EISCAT VHF-radar. Calculated
Havnes-parameters Λ reveal values which are much smaller than unity for
the large majority of observations.
Key words: Polar Mesosphere Summer Echoes;
Schmidt number; Volume reflectivity; Electron density
Presented by: Li, Qiang
A
new field campaign for tropospheric turbulence studies with the MU radar and
intensive insitu observations with RS92G Vaisala radiosondes.
Hubert
Luce 1, Richard Wilson 2, Francis Dalaudier 2, Noriyuki Nishi 3, Shoichiro Fukao 4, Masanori Yabuki 5, Hiroyuki Hashiguchi 5, Jun-ichi Furumoto 5, Yoshiaki Shibagaki 6, Tomoyuki Nakajo 4
1 South Toulon-Var University, La Garde, France
2 LATMOS-IPSL, UPMC Univ Paris 06, Univ. Versailles St-Quentin,
CNRS/INSU, Paris, France.
3 Division of Geophysics, Graduate School of Science, Kyoto
University, Kyoto, Japan
4 Department of Space Communication Engineering, Fukui University of
Technology, Fukui, Japan
5 Research Institute for Sustainable Humanosphere, Kyoto University,
Uji, Japan
6 Osaka Electro-Communication University, Negagawa, Japan
Soon
after their conceptions, ST VHF radars have been used simultaneously with
instrumented balloons for measuring atmospheric parameters. Intercomparisons
improved our knowledge on the radar backscattering mechanisms at VHF which, in
turn, provided some information on atmospheric dynamics and structures at
various scales. Various methods were then developed for retrieving small-scale turbulence
parameters from ST radars. However, the dominant sources and characteristics of
the turbulent events detected by the ST radars in the troposphere are still
poorly documented partly due to the lack of resolution of these instruments.
The
MU radar can be operated in range imaging (FII) mode so that a range resolution
of several ten meters can be achieved at a time resolution of a few tens of
seconds. For the first time, a field campaign was carried out in September
20011 for about three weeks with intensive balloon observations (59 RS92G
Vaisala radiosondes launched every three hours mainly during night periods).
The balloon data were devoted to the detection of turbulent events using an
original processing method based on Thorpe analysis of potential temperature
profiles (see the companion abstract by R. Wilson et al.). In addition, static
stability and Richardson number profiles could be estimated in the vicinity or
even within some turbulent layers. These data helped us to identify the nature
of the instabilities detected by the MU radar and the background atmospheric
conditions in which they occurred. Dynamical shear instabilities and convective
instabilities at cloud edges will be particularly addressed in this work.
Presented by: Luce, Hubert
Radar
and lidar observations in the summer mesosphere at Davis, Antarctica
Franz-Josef
Lübken 1, Josef Höffner 1, Bernd Kaifler 1, Timo Viehl 1, Ray Morris 2
1 Leibniz-Institute of Atmospheric Physics, Kühlungsborn
2 Australian Antarctic Division, Hobart, Australia
We
report the first simultaneous measurements of temperatures by a mobile Fe resonance
lidar and polar mesosphere summer echoes (PMSE) by a VHF
radar both located at Davis, Antarctica (69°S, 78°E). The lidar was installed
at Davis in December 2010 and measures temperatures in the iron layer, i. e.
approximately from 80 to 100~km. It is based on probing the Doppler broadened
resonance line of iron atoms and can operate under daylight conditions. Typical
values for temperature uncertainty, altitude and time resolutions are 3-5 K, 1
km, and 1 hour, respectively. The 55 MHz VHF radar performs measurements since
February 2003. Several hours of simultaneous lidar/radar observations are now
available from the Antarctic summer season 2010/2011. Ice particles in the
summer mesosphere can be detected by lidar (`noctilucent clouds', NLC) and also
create strong radar echoes known as PMSE. The existence of ice particles relies
on temperatures being lower than the frost point temperature. Temperatures
measured
by our Fe lidar are generally very low in the mesopause region but occasionally
show some unexpected features. For example, we sometimes find the mesopause at
significantly higher altitudes compared to similar latitudes in the northern
hemisphere. The VHF radar frequently detects PMSE. Temperatures are below the
frost point at PMSE altitudes assuming reasonable water vapor concentrations.
To our surprise PMSE were persistently absent at altitudes where temperatures are
much lower than the frost point. We note that (apart from low temperatures)
more ingredients are required for PMSE, for example, charged ice particles of
sufficient size, background electrons, neutral air turbulence etc. We present a
first overview of our measurements at Davis and discuss potential explanations
for the presence and absence of PMSE. We also compare with the general
circulation at lower altitudes and present first measurements of thermal tides
in Davis and comparison with corresponding NH observations.
Presented by: Lübken, Franz-Josef
An
FPGA-Based Wind Profiler Controller and Signal Processor
Charles
Martin , Eric
Loew , Chris Burghart , William Brown , Brad Lindseth
National Center for Atmospheric Research, Boulder, CO USA
Reconfigurable
computing and board level integration have experienced phenomenal advancement
in the last decade. These have enabled the functionality for radar system
control, signal processing and data acquisition to be migrated from rack-sized
systems and extensive custom circuitry onto off-the-shelf cards hosted in
generic computer workstations.
The
Software-Defined Digital Down Converter (SD3C) is a
complete radar processor built on a single commercial digital transceiver card.
The off-the-shelf card is based on a Field Programmable Gate Array (FPGA).
Multi-channel IF digitization, down-conversion, transmit pulse generation, and
digital timing signals are all provided by the PMC format card. The hardware
vendor supplies core firmware for controlling the hardware assets on the card
and integrating with the host operating system, and the developer simply
inserts application specific processing blocks within this framework. Flexible
firmware and host software implement a variety of signal processing tasks, such
as configurable filtering, data tagging, pulse coding/decoding, and coherent
integration. Other capabilities are possible. Reconfiguring the signal
processing behavior is achieved simply by loading different firmware. A single
card supports up to four channels of down conversion and one transmit
pulse output. Multiple cards can be combined to increase the number of channels
in the system.
The
SD3C system requirements and design are presented, with application to a newly
developed spaced antenna wind profiler. The functional components and their
interconnections are explored, with discussion of the development challenges
and lessons learned. Robust and well-designed software is the key to easily
deploying the processor in different profilers, and the SD3C host software
architecture is detailed. Performance measures and observational results are
given for the NCAR 449 MHz wind profiler.
Presented by: Martin, Charles
The
NCAR 449 MHz Modular Wind Profiler – Prototype and future plans
Stephen Cohn , William Brown , Brad Lindseth , Charles Martin
National Center for Atmospheric Research
NCAR
is developing a prototype modular wind profiler radar network to support
measurements for a broad range of meteorological studies. The new wind profiler
operates at 449 MHz, and will feature a low side-lobe antenna design, scalable
electronics and advanced signal processing methods. The modular design uses a
set of panels that can be operated together in various groupings to provide
flexible profiling capability that covers a range of altitudes and network
sizes. For example, the modules could be deployed as multiple small radars to
study the boundary layer over an extended area. Alternatively, the modules
could be combined together to create a more powerful and sensitive radar
capable of probing higher into the atmosphere.
A
prototype 3-module boundary layer system has been constructed and successfully
deployed during the recent PCAPS (Persistent Cold Air Pool Study) experiment in
the Salt Lake valley, and preliminary results will be presented. The system is
currently being expanded to 7 modules. Ultimately at least 19 modules are
envisioned, which would allow six (3-module) boundary layer profilers, or two
(7-module) mid-troposphere profilers, or one (19-module) full troposphere
profiler to be deployed. The new system would be deployed as an integrated
suite of instruments, with lidars and other in-situ and remote sensors, and is
intended to meet the diverse needs for studies of the atmospheric surface
layer, boundary layer, free troposphere, and tropopause region.
Presented by: Martin, Charles
Quality aspects of the measurements of a wind profiler in a
complex topography.
Mercedes
Maruri 1, Juan Antonio Romo 2, Leixuri Gomez 2
1 (1) Euskalmet/Tecnalia Unidad de Meteo. (2) UPV-EHU
University of the Basque Country.
2 UPV-EHU University of the Basque Country
It
is well known for the scientific community that some remote sensing
instrumentation have considered the assumption of homogeneity conditions in the
sample volumes to achieve a quality meteorological profile but generally, in a
complex topography and extreme meteorological conditions, this assumption is
faulty in the lower layers. This paper shows the results of a work that test
the homogeneity wind field over a boundary layer wind profiler radar sited in a
complex terrain at a coast, over different meteorological conditions. The
result of this work reveals how important is for quality purpose to know the
deviations of the assumption and evaluate its effect in the final product. This
information is useful as the starting point to look for the best alternative
that the system offers to build the wind profile. The methodology used is
crucial, taking into account that the amount of data is high and not all of
them are comparable, many decisions are assumed to avoid misinterpretation.
Finally the results are being considered to integrate in a quality algorithm
implemented at a product level.
Presented by: Maruri, Mercedes
A
Model Study on the Measurement Error of Wind Profiling Radar Observations in
the Atmospheric Boundary Layer
Makoto
Matsuda 1, Toshitaka Tsuda 1, Kuniaki Higashi 2, Jun-ichi Furumoto 1
1 RISH, Kyoto University
2 RISH, Kyoto University / Japan Meteorological Corporation
A
Wind Profiling Radar (WPR) with the Doppler Beam Swinging (DBS) is widely used
to measure the wind velocity in the lower troposphere regardless of weather
conditions, such as WINDAS of the Japan Meteorological Agency (JMA). For a
monostatic WPR with three or five antenna beams (hereafter called WPR3B and
WPR5B), we assume homogeneity of wind fields within the horizontal region of
antenna beam steering, which could, however, induce estimation error of the
wind velocity under disturbed conditions. In the planetary boundary layer below
about 2km, range difference inside the radar illuminating volume may not be
negligible, which produces a weighting for integration of scattered echoes.
Using
a numerical model, we investigated the measurement errors; (1) horizontal
inhomogeneity of winds, and (2) finite range volume effects. In particular, we
discuss advantages of a bistatic WPR (WPRB) with a pair of antennas for
transmission and reception.
We
first calculated the shape of the range volume assuming a realistic
specification of WPR operated on 1.3GHz, i.e., pulse width of 0.66microsecond
and 2m x 2m array antenna. We assumed a simple model of the horizontal wind
velocity with a linear shear along height (5m/s/km), and the wind shear is
changed at a certain height to 10m/s/km. The error of the horizontal wind
velocity is about 1 % for both WPR3B and WPR5B. The error increased to about 5%
at the altitude where the wind shear changed. For WPRB the measurement error
becomes smaller, because it determines the wind velocity in an overlapping
volume between two antenna beams, and therefore, the vertical resolution
becomes better.
In
order to investigate the effects of horizontal variations of the wind fields,
we used a realistic wind data provided from the Large Eddy Simulation(LES).
Under a quiet atmospheric state, no much differences
are seen in both methods. However, when atmospheric disturbance occurs, the
measurement error with WPR5B is less than that with WPR3B, because the former
is not affected by the linear horizontal gradient of horizontal wind field.
However, the linear horizontal gradient of vertical wind produces error even
for WPR5B. These measurement errors due to the horizontal gradient of winds do not
appear for WPRB.
We
estimated the measurement error for WPR, and found that WPRB provides a better
accuracy. As the system configuration, however, becomes more complicated for
WPRB, further investigation is needed to propose a better observation system.
Presented by: Matsuda, Makoto
Characteristics
of the “Hiccup” during the fall transition
Vivien
Matthias 1, Theodore Shepherd 2, Charles McLandress 2, Peter Hoffmann 1, Markus Rapp 1
1 IAP
2 University of Toronto
By
combining global satellite and high-resolution radar observation at Andenes
(69°N,16°E) and Juliusruh (54°N,13°E) with assimilated model data, the
characteristics of the disruption of the fall transition in the northern
hemisphere is investigated at stratospheric and mesospheric altitudes. With the
help of the global temperature observations from the Microwave Limb Sounder
(MLS) aboard the Aura satellite, the latitudinal and longitudinal dependence of
the “Hiccup” is investigated and the assimilated CMAM-DAS data are validated.
The composite pictures of wind, temperature and wave activity are also
considered and imply a correlation between the Hiccup and the onset up of the
polar vortex. The role of planetary-wave drag, gravity-wave drag and downward
control will also be analyzed in the dynamics of the fall transition Hiccup.
Presented by: Matthias, Vivien
Renovation
of the Aberystwyth MST radar: Technical issues
Richard
Mayo 1, John Bradford 2, Les Dean 3, Jon Eastment 2, Marco Hess 1, Eric Hibbett 1, David Hooper 2, John Jacobs 4
1 ATRAD
2 Rutherford Appleton Laboratory
3 Aberystwyth University
4 John Jacobs Consulting
In
early 2011, the Aberystwyth MST Radar underwent its first major renovation in
its 20 year lifetime. This principally consisted of replacing the components
which allow it to operate according to the Doppler Beam Swinging principle. The
design and installation work was carried out by ATRAD. The renovation
lead to a remarkable 28% increase in useful coverage for wind-profiling
purposes. This presentation will look at the technical aspects.
The original DBS system employed 100 phasing units which were distributed
throughout the antenna array. Each unit used electro-mechanical coaxial relays
to switch in lengths of cable to give a 3 bit binary phase shift. These relays
had a nominal lifetime of 1 million operations, which each relay typically
performed in a single year. Owing to their high cost and to their large
numbers, faulty relays were reconditioned rather than being replaced. The 6
monthly testing and reconditioning of these units became the major recurrent
maintenance task for the radar. Additionally, the 100 cables used to control
the relays were prone to weather and vermin damage. This contributed to radar
performance degradation and to maintenance cost.
The design of the replacement phasing units took the above experiences into
account. It aimed to minimise long-term maintenance time and material costs,
while actually improving the radar system capability. The new phasing units use
a microprocessor based design. They employ a standard 2.4 GHz industrial
protocol to communicate DBS and diagnostic information to a central controller
in the radar hut. The new phase shift relays cost just a few dollars each and
have a nominal lifetime of 20 million operations. This has allowed an improved
6-bit phase shift design to be implemented. The power and control signals to
the new phasing units are delivered through the existing radar RF cable
network. The original control cables have been removed entirely. In the case of
a failure, a phasing unit can be easily replaced with a spare before being
brought back to the workshop for test and repair. The new diagnostic
information has already proved itself to be useful for identifying problems in
other parts of the system. For example, it can indicate when one of the
transmitters has unexpectedly stopped operating.
Presented by: Mayo, Richard
New
Developments and Innovations in VHF Radar
Richard Mayo , Bronwyn Dolman , Gary Jonas , Iain
Reid , Jonathan Woithe
ATRAD P/L
A
number of new developments and innovations have recently been put into service
for both scientific and commercial radars produced by ATRAD. The most
significant of these is a combined Digital Transceiver system incorporating
Digital Exciter, Digital Receiver and Data Acquisition subsystems. The Digital
Transceiver supports radars operating in the MF, VHF and UHF bands. It has a
highly flexible architecture with the raw acquired data being delivered via a
gigabit data channel. The number of receiver channels can be expanded in
multiples of three and limited only by the data bandwidth of the computer
system processing or storing the data.
The Digital Transceiver is now used in MST, Boundary Layer, Meteor and
Ionospheric Radars and has been in use operationally for over 2 years. While no
systematic intercomparisons
have yet been completed, evidence suggests a typical increase of up to 20% in
meteor counts. This results in counts well over 30,000 per day on a 20kW All-sky meteor radar. The Digital Transceiver has
also produced marked improvements in the spectral results obtained from Doppler
radars, allowing for a very significantly improved ability to discern precipitation
returns from clear-air returns. Moreover, the results of an extended balloon
sonde inter-comparison against a 55 MHz ST-class Doppler radar and a 55 MHz
Boundary Layer radar demonstrate the ability to obtain reliable coverage down
to 500m for the Doppler radar and 300m for the Boundary Layer radar. The 10%
underestimation bias often observed on spaced-antenna radars operating the Full
Correlation Analysis has also been corrected.
Substantial effort has also been devoted to the development of improved
beam-steering systems. As a result it has been possible to all but eliminate
self-generated clutter in high power beam-steering applications and switching
systems. A further development of these beam-steering systems was used to good
effect in the upgrade of the Aberystwyth MST. This utilises a system of
intelligent phase controllers distributed through the array, powered and
controlled using ZigBee network communications down the RF feeder network. This
provides almost the same practical radar capability as a
radar using electronic beam-forming, but has the advantage of being able
to be retrofitted to older radars at a fraction of the cost of a complete
upgrade. The system also provides rich selfdiagnostic functions, automatically
sending warning messages and allowing a user to remotely assess identify the
nature of the fault and at which node the fault is occurring.
Presented by: Mayo, Richard
Australian
Government Bureau of Meteorology Next Generation Wind Profiler Network
Daniel
McIntosh
Australian Government Bureau of Meteorology
To
date, the primary source for obtaining wind data within the stratosphere and
troposphere has been with balloon flight observations; I.e. Radar tracked
balloon or GPS sonde. In its continued efforts to modernise and optimise its
composite observations network, the Australian Government Bureau of Meteorology
(BoM) has elected to procure and deploy radar wind profiler systems at various
remote locations around Australia. The goal is to implement a cost effective
observing system that provides high temporal resolution tropospheric wind data
for use in forecasting and nowcasting as well as input into Numerical Weather
Prediction (NWP). The supplier of the profilers is an Australian company
Atmospheric Radar Systems (ATRAD). The BoM will make use of two profiler types:
A low level Boundary Layer Profiler (BLP) and an upper level Stratospheric
Tropospheric Profiler (STP). All systems will be located within approximately
15 km of airports to provide support for aviation forecasting. The BLP systems
will utilise the Spaced Antenna (SA) technique and the STP systems will utilise
the Doppler Beam Steering (DBS) technique. ATRAD have implemented a bias
correction algorithm to correct for the speed bias associated with SA systems.
This
presentation will discuss the impetus for the network along with showing some
initial results. We will also outline plans for establishing a systematic
process for establishing some form of traceability of wind measurements
Presented by: McIntosh, Daniel
Atmospheric
radar reception using LOFAR technology
Derek McKay-Bukowski
Rutherford Appleton Laboratory
Traditional
radar and radio-astronomy methods have often been on diverging paths owing to
differences in frequency, sampling, control and the practicalities of equipment
implementation. However, with recent advances in digital signal transport and
processing, the techniques are showing convergence again. The LOFAR
(Low-Frequency Array) project is a massive phased-array radio-astronomy
programme, with many useful advances applicable to radar communities. This presentation
gives an overview of the LOFAR facility, and discusses recent developments
within the KAIRA (Kilpisjärvi Atmospheric Imaging Receiver Array) project which
will use LOFAR technology for VHF radar reception.
Presented by: McKay-Bukowski,
Derek
Eureka
meteor radar temperatures compared with Aura and SABER
Chris Meek 1, Alan Manson 1, Wayne Hocking 2
1 Institute of Space and Atmospheric Studies, University of
Saskatchewan,Canada
2 Department of Physics and Astronomy, University of Western
Ontario, Canada
The
meteor trail echo decay rates are analysed on site to provide daily temperature
at near 90Km. In order to get absolute temperature, either knowledge of the
pressure, or of the background temperature height gradient near 90Km is required
(Hocking,1999). The gradient is assumed to just depend
on latitude and time of year. Hocking et al.(2004) have
developed an empirical gradient model, which is used in the SKiYMET meteor
analysis. Here we look at the sensitivity of the resulting temperature to the
assumed gradient and compare the temperatures with daily Aura averages near
Eureka. The gradient model is also compared with Aura and SABER gradients. And
finally, long term oscillations in temperature and wind are compared.
Presented by: Meek, Chris
Mesosphere vertical velocity and tilts.
Chris Meek , Alan Manson
Institute of Space and Atmospheric Studies, University of Saskatchewan, Canada
Saskatoon
MF radar (MFR) analysis includes angle of arrival (AOA) phase and Doppler
velocity. The criteria for these are based on S/N only. We have been interested
in vertical velocity for years (J Atmos Sci., 46, 849-858, 1989) but dissuaded
by the difficulty in assuring that it is a vertical value, not due to a Tx beam or ionospheric scatterer tilts. With the wide beams
necessary
at
M,F an ionospheric tilt is the more likely cause of horizontal motion
contamination. The "best" tilt is defined as that which minimizes the
mean squared difference between measured and predicted (by tilt and horizontal
wind) Doppler velocities, and can be found by a least squares fit. Multi-year
statistics show that the tilts are seasonal and is
quite consistent year to year: about 4 degrees westward in summer (corroborated
to some extent by AOA phase) and 2 degrees southward in winter. In spring, especially,
and fall the tilts are small. Platteville MFR data are similar, which rules out
individual antenna array characteristics as a cause. Gravity waves travelling
against the wind (tilt up in the direction of propagation )
may be an explanation, at least for the summer feature,
Presented by: Meek, Chris
Advanced
Capabilities and applications of the new Digisonde DPS-4D at Juliusruh
Jens Mielich
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
The IAP field station in Juliusruh
(54.6°N 13.4°E, URSI code JR055) is well known for over 50 years of continuous
and high quality ionosonde data. Since the end of 2011 we have installed the
latest version of Digisondes, a DPS-4D, which provides a wide range of
technical and software innovations to speed up and improve the quality of
standard ionograms and save time for additional ionospheric measurements of
interest. We present results of first experimental experiences with E- and/or
F-region drift measurements by producing echo location skymaps and calculating
horizontal and vertical drift velocities of the ionospheric plasma above.
Beside
this scientific aspect of the Digisonde, it is routinely used for monitoring
and predicting ionospheric conditions especially for HF communication users.
For this purpose we plan to use the oblique sounding capabilities in the silent
reception mode to monitor neighbouring transmitting digisondes.
The
Juliusruh ionosonde station is part of the international Global Ionospheric
Radio Observatory (GIRO) and the European Digital Upper Atmosphere Server
(DIAS).
Presented by: Mielich, Jens
Case-study
of tropopause fold observation by MARA MST radar at
Wasa, Antarctica – comparison with ECMWF and WRF model data.
Maria Mihalikova , Sheila Kirkwood , Joel Arnault ,
Daria Mikhaylova
Swedish Institute of Space Physics
Tropopause
folds are one of the mechanisms of Stratosphere-Troposphere exchange, which can
bring ozone-rich stratospheric air to low altitudes. They can be observed in
mid–latitudes but also known to reach polar regions of
the Northern Hemisphere. With the help of MARA (Moveable Atmospheric Radar for
Antarctica) 54.5MHz MST radar, which was operated at the Swedish summer station
Wasa in Antarctica (73°S, 13°W) from season 2007 to 2011, and will be operated
at the Norwegian year-round station Troll (72°S, 2°E) from November 2011, tropopause
folds events were observed passing the radar site in polar regions of the
Southern Hemisphere. A case study of a tropopause fold observed by MARA during
the summer season 2010-2011, together with collocated ozone-sonde measurements,
will be presented. Comparison of observed changes in tropopause height during
this tropopause fold events with ECMWF and WRF model data simulations will be
made.
Presented by: Mihalikova, Maria
VHF/UHF
Radio-Wave Backscatter from Corrugated Sheets in the Stably Stratified
Atmosphere
Andreas
Muschinski
NWRA, CoRA Division
One
of the long-standing research topics in radio science is the relative
importance of turbulent vs. non-turbulent refractive-index fluctuations for
VHF/UHF backscatter from the optically clear atmosphere. The well-known
near-zenith echo intensity aspect sensitivity observed at VHF frequencies (50
MHz) has been explained as Fresnel scatter from non-turbulent, quasi-horizontal
“sheets,” which often dominates Bragg scatter from turbulent refractive-index
fluctuations. It appears to be less well understood, however, why there is
typically no aspect sensitivity at frequencies of 400 MHz and higher.
Here,
I present and discuss a theoretical analysis of the effects of small-scale
“sheet roughness” on the echo intensity as a function of radar wavelength and
zenith angle. The sheet roughness is characterized in terms of the
two-dimensional, horizontal wavenumber spectrum of the elevation fluctuations
of a sheet. The theoretical development builds on the Born
approximation of the backscattered wave and the Fresnel approximation of the
transmitted wave (see Doviak and Zrnic, Radio Sci., 1984; Muschinski, Radio
Sci., 2004).
Presented by: Muschinski, Andreas
Vertical
flow in atmospheric boundary layer observed by a lower
troposphere radar under clear air condition
Tomoyuki
Nakajo 1, Kenji Sasaki 2, Yuki Ogura 3, Yoichiro Saito 3, Hiroyuki Hashiguchi 4, Manabu D. Yamanaka 5, Shoichiro Fukao 1
1 Department of Electrical, Electronics and Computer Engineering,
Fukui University of Technology, Fukui, Japan
2 Department of Space Communication Engineering, Fukui University of
Technology, Fukui, Japan
3 Department of Electrical Engineering, Fukui University of
Technology, Fukui, Japan
4 Research Institute for Sustainable Humanosphere, Kyoto University,
Uji, Japan
5 Research Institute for Global Change, Japan Agency for
Marine-Earth Science and Technology, Japan
The
atmospheric boundary layer (ABL) is one of most important atmospheric layers in
terms of having a direct influence on our life, the detailed motion of
atmosphere, however, have not been fully investigated because of its immense
complexity.
One
of powerful tools for exploring ABL is Lower Troposphere Radar (LTR) which can
observe wind velocity in 3D from a few hundred meters to about ten km in
altitude with the range resolution of a few hundred meters and the temporal
resolution of a few minutes. There is no other observing tool which can realize
so highly resolved observation of ABL.
We
re-analyzed LTR data obtained at Shigaraki MU observatory in Japan from 2000 to
2006. In order to investigate the mean picture of ABL under clear air
condition, the daily average of wind velocity, echo power and spectral width
were calculated by using the data obtained in the case of clear sky. As the
results, it is clarified that the altitude of top of ABL reaches 1 km in winter
and more than 2 km in the condition of summer. In addition, we found that the
downward flow with the velocity of a few 10 cm/s grew up in all altitudes from
the minimum of observable altitude to top of ABL and was maintained in daytime
ABL. This downward flow was observed in all seasons, however, seemed to be
strongest in summer. Moreover, we also found that upward flow was almost always
observed after ABL dissipated at sunset.
Around
Shigaraki MU observatory, there are no high mountains which cause
mountain-valley wind that can reach 2 km in altitude,
therefore, we consider there may be another cause which determines the vertical
flows in ABL except for the effect of solar insolation or local topography.
Presented by: Nakajo, Tomoyuki
Adaptive
beamforming technique for accurate vertical wind measurements with
multi-channel MST radar
Koji
Nishimura 1,
Takuji Nakamura 1, Toru Sato 2, Kaoru Sato 3
1 National Institute of Polar Research
2 Graduate School of Informatics, Kyoto University.
3 Department of Earth and Planetary
Science, The University of Tokyo
Aspect-sensitive
backscattering of the atmosphere causes a small error in an effective
line-of-sight direction in vertical beam observations leading to a serious
degradation in vertical wind estimates due to contamination from horizontal
wind components. An adaptive beamforming technique for a
multi-channel MST radar is presented which enables us to measure the
vertical wind velocity with higher accuracy by adaptively counter-steering the
reception beam against the imbalance of aspect-sensitive reflectivity pattern. The
technique employs the norm-constrained direction-constrained minimization of
power (NC-DCMP) algorithm which provides not only robustness but also a higher
accuracy than basic DCMP algorithm under realistic conditions.
Although
the technique decreases the signal-to-noise ratio (SNR), the amount is
controlled and bound at a specified level by the NC. In case the decrease of
-3dB can be accepted in a vertical beam observation, in which usually much
higher SNR is obtained than in oblique beams, the maximum contamination is
suppressed to 1/10 at its maximum even if the possible severest imbalanced
aspect sensitivity exists.
Presented by: Nakamura, Takuji
Long-term
variability and trends of mean winds in the mesosphere and lower thermosphere
within ±22°
Venkateswara
Rao Narukull
1, Toshitaka Tsuda 1, D. M. Riggin 1, S Gurubaran 2
1 RISH, Kyoto University, Uji, Japan
2 EGRL, Indian Institute of Geomagnetism, Tirunelveli, India
We
studied the long-term variability of mean zonal and meridional winds in the
Mesosphere and Lower Thermosphere at seven locations; Kauai (22°N, 154°W),
Tirunelveli (8.7°N, 77.8°E), Christmas Island (2°N, 157°W), Koto Tabang (0.2°S,
100.3°E), Jakarta (6°S, 107°E), Pameungpeuk (7.4°S, 107.4°E), and Rarotonga
(21.2°S, 159.7°W). Locations with nearly similar latitudes such as Christmas
Island and Koto Tabang, and Jakarta and Pameungpeuk are treated as single
location and the data are appended at each latitude to
get the long-term data. The mean meridional wind shows a distinct annual
oscillation at all locations. They also show opposite long-term trends at ~ ±8°
with the winds changing from northward to southward at Tirunelveli (8.7°N) and
from southward to northward at Jakarta and Pameungpeuk (~ 7°S). The zonal wind
shows a distinct semiannual oscillation at all locations. The annual mean zonal
winds within ±8° are westward biased and are eastward biased outside. The zonal
winds does not show any significant long-term trends.
Furthermore, we use regression analysis to obtain linear trends and trends
associated with forcing due to Quasi Biennial Oscillation (QBO), Southern
Oscillation Index (SOI), and Solar Cycle (SC).
Presented by: Narukull,
Venkateswara Rao
Momentum
Flux Determination using the Multi-Beam Poker Flat Incoherent Scatter Radar
Michael
Nicolls 1, David Fritts 2, Diego Janches 3, Craig Heinselman 1
1 Center for Geospace Studies, SRI International, Menlo Park,
California, USA
2 Colorado Research Associates, NorthWest Research Associates,
Boulder, Colorado, USA
3 NASA / Goddard Space Flight Center, Greenbelt, Maryland, USA
We
present an estimator for the vertical flux of horizontal momentum with
arbitrary beam pointing, applicable to the case of arbitrary but fixed beam
pointing with systems such as the Poker Flat Incoherent Scatter Radar (PFISR).
This method uses information from all available beams to resolve the variances
of the wind field in addition to the vertical flux of both meridional and zonal
momentum, targeted for high-frequency wave motions. The estimator utilizes the
full covariance of the distributed measurements, which provides a significant
improvement over the direct extension of previously developed techniques. We
find that for the PFISR experiment, we can construct an unbiased and robust
estimator of the momentum flux if sufficient and proper beam orientations are
chosen, which can in the future be optimized for the expected frequency
distribution of momentum-containing scales. We address the effects of beam
pointing errors on the estimator, which comes as a result of the finite
beamwidth (1 deg x 1.5 deg referring to the +/-3-dB pattern) of PFISR, and find
that expected biases for the specific geometry considered are no more than a
few m^2/s^2. We apply the estimator to PFISR mesospheric measurements (60-85 km
altitude), and show expected results as compared to mean winds and in relation
to the measured vertical velocity variances.
Presented by: Nicolls, Michael
High-latitude
Observations of Atmospheric Gravity Waves in the Mesopause Region
Dominique
Pautet 1, M.J. Taylor 1, Y. Zhao 1, W.R. Pendleton Jr 1, Peter Hoffmann 2, Werner Singer 2
1 Center for Atmospheric and Space Science (CASS)
2 Institute of Atmospheric Physics (IAP)
Atmospheric
gravity waves propagating from the troposphere up to the lower thermosphere
play a key role in the thermal structure and large-scale circulation of the mid-atmosphere.
These waves have been extensively studied using wide-angle CCD imagers, but
mostly from sites located at low and mid-latitudes. High-latitude observations
are more difficult due to the permanent twilight during the summer months and
the frequent presence of auroras contaminating the airglow signatures during
the winter period.
To
better quantify the effects of gravity waves at MLT (mesosphere lower
thermosphere) heights (~80-100 km) over high-latitude sites and improve the
knowledge on their propagation characteristics, and geographic variability,
several Utah State University optical instruments were recently deployed at the
ALOMAR Arctic facility (69.3°N), and at the Amundsen-Scott South Pole Station
(90°S).
During
the 2009-10, a wide-angle (~120°) broadband infrared (0.9-1.7mm) InGaAs camera
was operated at ALOMAR. It provided key measurements to study the main
characteristics of the short-period gravity waves propagating over the
observatory, including horizontal wavelength, propagation direction, observed
period and phase speed. In November 2010, this instrument was upgraded to
measure the mesospheric temperature using the ratio between the OH (3,1) and (4,2) bands.
The
characteristics of the short-period gravity waves and their effects and response
to the MLT region dynamics will be discussed and compared with observations
from other high-latitude sites.
Presented by: Pautet, Dominique
Apparent
electron density modulation under RF heating at EISCAT UHF and its application
for estimating the electron-ion temperatures ratio
Henry
Pinedo 1, Cesar La Hoz 1, Ove Havnes 1, Mike Rietveld 2
1 University of Tromsø, department of Physics and Technology
2 EISCAT, Heating Division Ramfjordmoen
In
a co-located campaign with UHF radar and Heating EISCAT facilities on June 7
2010 in Tromsø¸-Norway, standard EISCAT analysis show an apparent electron
density modulation during heating-on times. The modulation is fairly evident at
heights above 90 km of altitude and is manifested as a depletion of density of
approximately 40% respect to the background level during heating-off times. The
increase of electron temperature in a controlled way is an expected result of
artificial heating perturbation. However, the amount of energy required to
produce density modulations sensible to radar systems on the ground is much
more than what the HF can produce and transfer to the plasma. The associated
plasma transport process due to pressure gradients induced by electron
temperature variations is slowed down by the ion mass according to ambipolar
diffusion. Therefore, the plasma transport time scale to produce measureable
plasma depletion is larger than the current 20sec Heating-on time. The apparent
electron density modulation is attributable to how the corresponding parameters
have been estimated. The assumed criterion of equal temperature for electrons
and ions inside the involved region is not valid under heating conditions. This
situation provides an opportunity for simple and reliable estimation of Te/Ti ratio
during heating-on times, based on a density modulation-less process using the
radar equation.
Presented by: Pinedo, Henry
Comparison
of mesospheric gravity wave momentum fluxes derived by MF Doppler radar and
meteor radar measurements at 69°N
Manja
Placke , Peter
Hoffmann , Markus Rapp , Werner Singer , Ralph Latteck
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
The
gravity wave momentum flux is an essential parameter to study the dynamics of
the middle atmosphere. With the Saura MF radar (69°N, 16°E) narrow beam wind
measurements can be performed in the upper mesosphere from about 60 to 100 km.
Running in the Doppler Beam Steering (DBS) mode, gravity wave momentum fluxes can
be determined from radial velocity variations of coplanar beams by using the
method from Vincent and Reid (1983). The co-located Andenes meteor radar offers
wind measurements from reflections at ionization trails of ablating meteoroids
between about 80 and 100 km. Gravity wave momentum fluxes can simultaneously be
determined together with wind variances by applying a regression method
proposed by Hocking (2005).
In
order to validate these observations, we investigate the momentum fluxes with
both methods. Using several selection criteria for the calculations we compare
both mean profiles as well as the day-to-day variation of the momentum fluxes
obtained from these two independent instruments and methods for a case study in
April 2011.
Presented by: Placke, Manja
Chemistry
of meteor trail formation
John Plane 1, Wuhu Feng 2, Diego Janches 3
1 School of Chemistry, University of Leeds
2 Schools of Chemistry and Earth & Environment, University of
Leeds
3 Godddard Space Flight Center, NASA
This
paper will discuss three aspects of meteor trail chemistry. First, the ablation
process itself will be considered: what are the important thermodynamic and
kinetic processes which control the ablation rates of different meteoric
constituents, how well do we understand these processes; and how can important
uncertainties be resolved, perhaps through laboratory simulations? The current
version of the Leeds Chemical Ablation Model (CABMOD) appears to predict the
process of differential ablation quite well, as evidenced by satisfactorily
modelling the time evolution of meteor head echoes. However, combining this
model with an astronomical model of dust sources in the solar system to derive
the Meteoric Input Function (MIF) for the earth reveals a significant problem
regarding the relative injection rates of Na, Fe and Ca atoms into the
atmosphere.
This
leads onto the second topic of the paper, the nature of the ablation products
and how they evolve with time. Hyperthermal collisions with air molecules
should lead to complete atomization of any molecular products, as well as
significant ionization (the resulting electrons are observed by meteor radars).
Laboratory studies of metal ion-molecule reactions have provided a much better
understanding of how the metal ions and electrons will react as they diffuse
into the ambient atmosphere and encounter atomic O and O3. This can
influence the apparent diffusional time-constant of a meteor trail, which is
sometimes used to infer the air density and hence temperature in the vicinity
of the trail.
The
third topic is the formation of meteoric smoke. There is a long-standing
assumption that meteoric ablation products diffuse so rapidly into the
background atmosphere that they do not condense to form metal silicates within
the trail itself. While this appears to be a valid assumption, metal silicate
molecules (e.g. MgSiO3, MgFeSiO4) are so stable that they
could evaporate at temperatures around 2000 K. If most of
this evaporation occurred into the trail behind the meteoroid, then a fraction
of these molecules might survive intact, leading to permanent sinks for these
metals and providing "seeds" for smoke formation. While this
is only a conjecture, it would help to explain the relative inputs of Na to Fe
in the upper mesosphere.
The
final aspect of meteor trail chemistry to be discussed is the role that these
metal silicates play in the charged state of the D region, where there
is now growing evidence that they are often largely responsible for the
observed depletion of electrons relative to positive ions below 90 km.
Presented by: Plane, John
Satellite
observations of gravity wave momentum flux and interpretation by global
ray-tracing modeling
Peter Preusse , Manfred Ern , Silvio Kalisch
Forschungszentrum Jülich, IEK-7
Temperature
measurements of the infrared limb sounder SABER are analyzed for GWs in the
altitude range 25 to 100 km. In a first step global scale structures up to
wavenumber 6 are removed by a space-time spectral analysis. Residual vertical
profiles are analyzed by a combination of MEM and sinusoidal fits. Using
profile pairs with an along-track distance of less than 300~km, absolute values
of GW momentum flux are determined. Global distributions are interpreted in
terms of various sources. Gravity wave maxima from the subtropics shift
poleward as the GWs propagate upward and also the polar vortex maximum widens
widen with altitude. Time series are discussed for the annual cycle, QBO and
long-term variations. The measurements are compared to ray tracing simulations.
Finally, an outlook to proposed satellite missions is given.
Presented by: Preusse, Peter
Differences
in the Atmospheric Boundary Layer (ABL) characteristics between active and
break spells of the monsoon
A. Sandeep , T. Narayana Rao
National Atmospheric Research Laboratory
The
Atmospheric Boundary Layer (ABL) is the layer that is directly influenced by
the presence of the earth’s surface and its forcing. The surface forcing
depends on several factors starting from geography to surface characteristics
and to dynamics of the atmosphere at lower levels. Therefore, one would expect
significant changes in the ABL characteristics during rainy days and non-rainy
days. In this regard, it is important to remember that the rainfall during the
monsoon season doesn’t occur as a continuous deluge; rather occurs in spells
(known as active spells). Also, recent studies have shown that the background
thermal and dynamical characteristics of the atmosphere near the surface and
aloft are different in different spells of the monsoon. Any change near the
earth’s surface modifies the boundary layer structure and its evolution.
Unfortunately, there was no documentation on these changes in different spells
of the monsoon, partly due to the paucity of continuous high-resolution data to
study the intraseasonal differences in the evolution of ABL. Therefore, the
main aim of this study is to understand the differences in the winds and
turbulence characteristics in different spells of the monsoon using
high-resolution measurements made by a UHF radar at Gadanki.
The present study also includes statistical characteristics of wind speed and
direction, vertical velocity, SNR and spectral width (a measure of turbulence)
in different spells of the monsoon. Special emphasis has been given to
understand differences in low level jet characteristics between spells.
Presented by: Rao, T. Narayana
First
three - dimensional observations of polar mesosphere winter echoes: Resolving
space - time ambiguity
Markus
Rapp , Ralph
Latteck , Gunter Stober , Peter Hoffmann , Werner Singer , Marius Zecha
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
We
present the first three‐dimensionally resolved observations of polar mesosphere
winter echoes obtained with a 25 beam‐experiment covering a volume of about 50 km in diameter
(horizontal distance) at altitudes between 65 and 85 km. This allows us to
resolve the classical space time ambiguity of single beam observations and reveals
that the echoing structure was tilted in the East–West direction but showed no
considerable tilt in the North–South direction. The Doppler shifts derived from
the 24 off‐zenith beam directions are
consistent with the mean background wind measured independently by a co‐located MF‐radar. The time development of the 3‐D echo‐pattern is consistent with
scattering structures that follow the constant phase lines of a medium
frequency gravity wave that is propagating against the mean flow. Wave
parameters derived from these observations are independently confirmed by the
analysis of co‐located wind measurements with the
aforementioned MF‐radar.
Overall, the observed echo morphology in time and space is reminiscent of
gravity wave breaking which is known to lead to a maximum of
turbulence activity that moves with the phase of the wave.
Presented by: Rapp, Markus
The
Tropospheric cooling and the Stratospheric warming at
Tirunelveli during the Annular Solar Eclipse 15 January, 2010
Kusuma G.
Rao 1, Nelli Narendra Reddy 1, Raj Kumar Choudhary 2
1 Atmospheric Science Programme, Indian Space Research Organization,
New BEL Road, Bangalore 560094, India, kusuma@isro.gov.in
2 Space Physics Laboratory, Vikram Sarabhai Space Center,Thumba PO,
Trivandrum - 695002, India
The
transition region between the troposphere and the stratosphere is of concern to
climate scientists as it is crucial in determining the water vapour and other trace
gases transport between the two regions, which inturn determine the radiative
warming and cooling of the troposphere and the stratosphere. To examine, the
troposphere and stratosphere coupling interms of tropospheric cooling and
stratospheric warming, a major experiment facility was set up for upper air and
surface measurements during the Annular Solar Eclipse (ASE) of January 15, 2010
at Tirunelveli (8.72 N, 77.81 E) located in 100% eclipse path in the southern
peninsular India by installing GPS radiosonde system, an instrumented 15 m high
Mini Boundary Layer Mast, an instrumented 1 m high Near Surface Mast (NSM),
radiation and other sensors at the surface. The ASE of January 15, 2010 was
unique being the longest in duration (9 min, 15.3 sec) among the similar ones
that occurred in the past.
Upper
air measurements were made by launching six balloons everyday to study the
contrast in eclipse impact and as well to study the evolution of atmospheric
thermal and wind structure. Striking result here is the net cooling in the
troposphere with peak cooling of ~ 5 oC at ~ 15 km and intense
warming in the stratosphere of ~ 7 oC at ~ 19 km in the vertical. On
the eclipse day, an unusual marching in temperature structure is observed with
a warm layer seen from near surface to 1 km height in the vertical and a cool
layer subsequently up to ~19 km height with coldest temperature crossing ~ -75 oC
at ~ 17.5 km during the ASE in comparison with the temperature variations
outside the eclipse time window. Cooling of the Troposphere as the eclipse
advanced and the revival to its normal temperature is clearly captured in upper
air measurements. Lower stratospheric waves are observed in upper air wind
measurements during the ASE window. Further analysis is being carried out to
quantify the wind variations.
Stratospheric
warming may be attributed to the indirect thermodynamic influence associated
with variations in stratospheric circulation induced by net cooling in the
troposphere. For instance, the maximum warming of the lower stratosphere could
be due to occurrence of maximum downward motion at that level. Also our aim
here is to understand the possible links between the lower stratospheric
warming and the surface layer parameters.
Presented by: Reddy, Nelli
Narendra
Meso
highs and Meso lows observed over the Indian region during Deep
convective conditions
Nelli
Narendra Reddy ,
Kusuma G. Rao
Atmospheric Science Programme, Indian Space Research Organization, Bangalore,
India
An
attempt has been made here to understand the impact of deep convection embedded
in Mesoscale Convective Systems (MCS) of Indian summer monsoon in inducing
surface pressure variations, such as meso highs and lows, leading to localized
thunderstorms. Data utilised for the analysis is from PRWONAM meso-network of
instrumentation, namely, Instrumented micrometeorological towers (50 m high, 15
m high), AWS, Micro Rain Radar, GPS Radiosondes along with MST Radar, LAWP,
Disdrometer at NARL, Gadanki. Also merged IR brightness temperatures, TRMM 3B42
rainfall and COSMIC RO profiles data for the May to September period in the
years, 2000 and 2011 are used in the analysis. The results are presented for
six Case studies for convective events at Dibrugarh (27.44 N, 94.89 E) on 22
July, 2009, at Gadanki (13.27 N, 79.10 E) on 18 November, 20095 and 5, 12 July,
2010, at Bangalore at two locations (12.54 N, 77.22 E; 12.55 N, 77.30 E) on 19
April, 2011 and at Ranchi (23.25 N, 85.25 E) on 5 May, 2011. The major findings
from the analysis carried out here are the following. 1. Frequency of
occurrence of Very Deep (BRT < 210 K) to Deep (240 K < BRT < 210 K)
cloud systems at Bangalore location during April-September months of 2009 and
2010 is observed to be maximum between 18hrs to 06 hrs (local time IST). 2. Precipitating
Deep clouds caused a significant dip in the surface temperature by ~10 oC and a
sharp rise in wind speed by 5 – 8 m s-1 and pressure anomaly of ~ 2 mb along
with a drop in surface specific humidity by ~ 2 gm kg-1 and surface equivalent
potential temperature by ~ 7 K. A sudden change in the wind direction is
observed during the passage of convective lines of MCSs. 3. A reduction in CAPE
by ~ 1200 J kg-1, shrinking of Tropical Tropopause Layer (TTL) and cooling of
Cold Point Tropopause (CPT) are noteworthy observations inferred during the
deep convection at Gadanki. 4. The observed pressure perturbations during the
Case studies are associated with strong downdraft and updrafts in the MST radar
measurements. Possible explanations for the observed pressure perturbations are
being explored in terms of hydrostatic effects like latent heating in updraft
and non hydrostatic effects like low level convergence and strong downdrafts.
Presented by: Reddy, Nelli
Narendra
Characterisation
of Deep Convective System of Indian Summer Monsoon using spaceborne Cloud
Profiling Radar on CloudSat
M. Muhsin 1, Rao Kusuma 1, Nelli Narendra Reddy 2
1 Atmospheric Science Programme, Indian Space Research Organization,
Bangalore, India
2 Indian Space Research Organisation HQ.
It
is well known from satellite imageries that Indian Summer monsoon variability
is a manifestation of the propagating deep cloud systems embedded in the
continental and oceanic Tropical Convergence Zones (TCZ) .
CloudSat
is the first satellite carrying spaceborne millimeter radar called the Cloud
Profiling Radar (CPR), and was launched on April 28, 2006 as a part of A-train
constellation. Cloud Profiling Radar (CPR) measures the vertical structure of
clouds and precipitation primarily through 94 GHz radar reflectivity. CloudSat
standard data products are produced at each CloudSat profile location. Each
Profile consists of 125 vertical bins of width ~ 240 meters. Each CloudSat
profile is generated over a 160 millisecond interval which corresponds to a 1.1
km along track distance. With orbital motion, this produces a footprint which
is approximately 1.4 km (across-track) by 2.5 km (along track). A granule of
CloudSat data (one orbit) consist of ~ 40000 profiles. CloudSat data products
are radar reflectivity, cloud type, cloud liquid water content, cloud ice water
content, cloud optical depth, atmospheric radiative flux and heating rate, etc.
Here
an attempt is made to characterize Deep Convective System of Indian summer monsoon
region using the above mentioned CloudSat data products. The region taken for
study made here is [10S:40N-50E:110E]. As a first step, we gridded this region
in to 30 grids of 10 X 10 degree resolution. Using 2B-CLDCLASS data product,
relative percentages of occurrence of deep convective systems has been
calculated by counting only the deep convective cloud profiles for the monsoon
months of the year 2009 for all the 30 grids. It has been seen that major
CloudSat observed zones of deep clouds (~70-100%) during the August-September
months are in the oceanic convergence zones of Indian Ocean. At the same time,
the percentage of occurrence of deep clouds over the central parts of India and
Head, Bay of Bengal is observed to be relatively less. This result indiactes
that reverse Hadley circulation was stronger during 2009. The CloudSat observed
zones of deep cloud system indicate that oceanic TCZ was intense leading the
monsoon to be weaker and hence the year 2009, a worst drought year.
Liquid
and ice water content will be extracted to characterize the monsoon deep cloud
systems along with the collocated data sets from TRMM. Simultaneous data from
PRWONAM meso-network are being used to characterize the Deep Convective systems
of the monsoon region.
Presented by: Reddy, Nelli
Narendra
Impact
of Total Solar Eclipse on troposphere and stratosphere thermal and wind
structure at Dibrugarh on 22 July, 2009
Kusuma G. Rao , Nelli Narendra Reddy
Atmospheric Science Programme, Indian Space Research Organization, Bangalore,
India
For
the first time, an experiment facility was set up at Dibrugarh (27.45N, 94.92E)
in the north-eastern Indian region to make Micro-meteorological and Upper
measurements for studying the near surface and tropospheric response to the
Total Solar Eclipse (TSE) of 22 July, 2009 by installing an instrumented Mini
Boundary Layer Mast (MBLM, 15 m high), GPS radiosonde system and several ground
sensors. The duration of the eclipse was for 02 h 09 m 37.5 s, with a totality
of 03 m 32.1 s at Dibrugarh. The Surface layer is characterized on cloudy,
rainy and clear sky days in all the observed surface layer parameters. The
Incoming SW radiative flux reduced drastically by ~63-85% at its peak during
the cloudy conditions associated with blanketing effects of clouds, against the
clear sky conditions. The Solar eclipse is characterised by a dip of 25.8 W m-2 in the Incoming SW radiative flux from its
peak value during the PSE-1 to near zero values with total cut off
during the TSE.
A
near constancy in temperature at ~ 27.3 0C at 4 m height is noted
over a short time window around TSE. A decrease in the wind speed with a
reversal in the average wind direction from north-westerlies during the PSE-1
through south-westerlies during the TSE to south-easterlies during the PSE-2 at
4 m height is noticed.
Upper
air measurements revealed near surface inversion in temperature of ~1.3 0 C
in the height region of 240-370 m above the surface at the TSE timings
comparable with the nocturnal inversion observed during the experiment period.
A warm layer has been observed in the lower troposphere between 400 m – 2.6 km
in the vertical during the eclipse with maximum warming by 0.75 oC
at 1.8 km. Mid troposphere cooling in the region from
2.6 km to 12 km is observed during eclipse with maximum cooling of ~ 4.8 oC
at ~ 8.8 km height.
Wind
measurements indicatedthat easterlies prevailed from close to surface up to ~
1.5 km height in the vertical with reversal to westerlies beyond up to ~5 km
height. A low wind transition region is found between 5~10 km with relatively
stronger easterlies prevailing at higher heights. On the eclipse day of 22
July, 2009, a wave like pattern with wavelength ~2.3 km is observed in wind
speed in the height region, 18.3 – 20.6 km above the Earth’s surface.
Presented by: Reddy, Nelli
Narendra
Shrinking
of Tropical Tropopause Layer during the Disturbed Convective conditions over
the Bay of Bengal with JASMINE Measurements
Kusuma G.
Rao , Nelli Narendra Reddy
Atmospheric Science Programme, Indian Space Research Organization, New BEL
Road, Bangalore 560094, India, kusuma@isro.gov.in
The
Indian summer monsoon variability on the intra-seasonal time scales of 30-40
days and on the “Active” and “Break” cycles, is
largely accounted by the varying convective activity over the Bay of Bengal.
Very little is known about the impact of intense convection of the monsoon
region on the upper tropospheric and lower stratospheric circulation systems
and on the dynamics/thermodynamics of the Tropical Tropopause Layer, a
transition region from troposphere to stratosphere. Moistening and drying of
TTL, being a region of Low Background Humidity (humidity drops by four orders
of magnitude from the surface to TTL), locally or globally, is a key factor for
the Global Climate Change observed. This is because the Long Wave Radiative
fluxes show strong sensitivity to humidity variations in the region. While
there are extensive studies to show significant impact of convection on TTL for
Pacific, Indonesian and other regions, there are very few studies for the
monsoon region on the impact of organized monsoon convection on the Tropopause
layer dynamics and thermodynamics
Thus
the question we tried answer here is, what is the impact of organized
convection of Bay of Bengal, sustained over a few days, on the Tropopause
Layer? An effort is made here to answer this question by carrying out analysis
of the measurements available from the International field programme, JASMINE
(Webster et al., 2002) conducted in the year 1999 (April to June and September)
over the Bay of Bengal with the research vessel, the NOAA Ship Ronald H Brown
using GPS radisondes, cloud radar, instrumented mast, etc . Thus, our chief
objective here is to discuss the nature of the TTL variations during the periods
of organized convection over the Bay of Bengal. Also our aim here is to
understand the possible links between the TTL variations and the surface layer
parameters.
Based
on JASMINE data analysis, we inferred here that, during convective conditions,
both the lowering of Cold point tropopause temperature and the corresponding
CPT Altitude (CPTA) are significant, unlike in the normal case determined by
normal temperature lapse rates. TTL thickness shrinks during the convective
conditions due to lowering of the upper boundary of TTL (CPTA) and deepening of
the lower boundary (LRMA, Lapse Rate Minimum Altitude) of the TTL. The result
that Unlike Normal cases are associated with higher CAPE and higher surface
equivalent potential temperatures lead to explain the possible mechanisms
underlying the observation made here of CPT cooling at relatively lower
altitudes.
Presented by: Reddy, Nelli
Narendra
Impact
of Meso-Network Observations on prediction of Extreme Rain Events of the Indian
Summer Monsoon during PRWONAM
Kusuma G.
Rao 1, Rani Jacob 1, Nelli Narendra Reddy 2
1 Atmospheric Science Programme, Indian Space Research Organization,
New BEL Road, Bangalore 560094, India, kusuma@isro.gov.in
2 Indian Space Research Organisation HQ.
The
changing rainfall pattern of the Indian summer monsoon with increasing trend in
Extreme Rain Events attributed to the unequivocal warming of the environment is
a subject of concern in recent times.
Based
on TRMM 3B42 data for the twelve years period, 1999-2010, preferred regions of
occurrence of Extreme /Intense Rain Events are examined over both the Indian
Land and the adjoining Sea with the observed rain events constructed every day.
The classification in to Moderate, Intense and Extreme Rain Events (MRE, IRE,
and ERE) are based on the thresholds devised on the accumulated rainfall of the
events normalised with their respective duration for the homogeneous Central
Indian region. Three broad prominent regions have been identified for
occurrence of EREs, namely, the 1. West-Central Parts of
India and the adjoining Arabian Sea [WCI region], 2. Central
and North-Central parts of India [CI region] and 3. North-Eastern parts
of India and the adjoining Bay of Bengal [NEI region]. The striking inference
is the shift in preferred regions of EREs observed from NEI region to WCI
region with the trends reversed in the study period. Most of these ERE/IRSs are
associated with short lived mesoscale weather systems.
Accurate
weather prediction in the tropics using dynamical models is a challenging task
today. PRWONAM (Prediction of Regional Weather with Observational Meso-Network
and Atmospheric Modelling), a unique national science mission of Indian Space
Research Organization, initiated in the year 2006, aimed at resolving and
modelling the mesoscale weather systems of the Indian region.The PRWONAM
meso-network of Instrumentation all over the Indian land region, consists of
AWS, GPS radiosondes, Micro-meteorological towers (50 m high), Mini Boundary
Layer Masts (15 m high), ST Radars/Micro Rain Radars, etc. Several field
campaigns have been carried out to observe and predict Extreme Rain Events.
Model
experiments to predict Extreme rain Events of the Indian region have been
carried out with NCAR Weather Research Forecast (WRF) model to examine the
impact of meso-net data assimilation in to NCEP GFS initial conditions. It is
established beyond doubt that predictions significantly improve with meso-net
data assimilation. Also, model experiments are conducted to understand the
processes underlying the genesis of Extreme Rain Events by comparing the model
physics based scaling laws of surface fluxes with the observed behaviour
arrived at in measurements from 50 m towers.
Presented by: Reddy, Nelli
Narendra
60
years of meteor radar at Adelaide
Iain Reid
University of Adelaide
With
the exception of the use of very high power incoherent scatter radars to study
meteors, meteor radar development at Adelaide typifies that of the technique
around the world, and it is now almost 60 years since the first measurements of
atmospheric winds in the 75-105 km height region were made using meteor radar
at Adelaide. This was in June 1952. Construction of this system commenced in
1950, and the first photographic recordings showing Doppler beats were recorded
in December 1951. Winds were measured by observing the drift of meteor trails
using photographic recording and subsequent manual analysis. This system
operated until March 1955. In 1958 a field site was established at St Kilda
north of Adelaide, and meteor work continued there from this time until the
mid-1970s. Meteor work using the BP MF radar was first undertaken during
1969-72, and continued through the 1990s. In the early 1990s, narrow beam
meteor work resumed on the ST VHF radar at the Buckland Park field site, also
north of Adelaide. In the late 1990s meteor work using small pulsed operation
VHF radar systems started in Adelaide.
These
systems have now become commonplace, and considerable progress has been made in
exploiting the meteor technique to measure winds and temperatures in the 80 to
110 km height region, and to measure meteor velocities. In this paper, a brief
history of the development of the technique at Adelaide, and some of these
recent developments are presented and discussed.
Presented by: Reid, Iain
New
Equipment and Data Processing Techniques at the University of Adelaide Field
Site
Iain Reid 1, Bronwyn Dolman 2, Joel Younger 3, Jens Lautenbach 4, Andrew MacKinnon 3
1 University of Adelaide & ATRAD Pty Ltd
2 ATRAD Pty Ltd
3 University of Adelaide
4 Leibniz Institute of Atmospheric Physics
Buckland
Park (BP) is the University of Adelaide field site, located 36 km north of the
city of Adelaide, and the University campus. BP is currently home to a 55 MHz
BL Profiler, 55 MHz ST Profiler, MF Profiler, 55 MHZ Meteor Radar, 55 MHz
mini-BL Profiler, RASS, OH and 02 spectrometer,
three-field photometer and an all-sky airglow imager. A
Rayleigh Lidar and SuperDARN radar are currently under development.
Recent
upgrades at BP include new ATRAD digital transceivers on the BL, ST and meteor
radars, and a new ATRAD beam steering unit on the ST profiler. The BL and ST
profilers are also running with new quality control algorithms. Improvements to
the BP systems have resulted in new capabilities, such as ST wind estimation
down to 500 m, and clean raindrop size distribution retrievals from 500 m to
the freezing level on both the BL and ST systems. Ice retrievals above the
freezing level are also now possible with the ST system. BP developments and
new results will be discussed.
Presented by: Reid, Iain
Validation
of the receiving pattern of the MAARSY phased antenna array
Toralf
Renkwitz , Ralph
Latteck , Werner Singer , Gunter Stober
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
In 2009/2010 the Leibniz-Institute
of Atmospheric Physics (IAP) installed a new powerful VHF radar on the island
Andoya in Northern Norway (69.30°N, 16.04°E). The Middle Atmosphere
Alomar Radar System (MAARSY) is designed for improved
studies of the Arctic atmosphere with high spatial and temporal resolution in
the troposphere/lower stratosphere and in the mesosphere/lower thermosphere.
The monostatic radar is operated at 53.5 MHz with an active phased array
antenna consisting of 433 Yagi antennas. Each individual antenna is connected
to its own transceiver with independent phase control and a scalable power
output of up to 2 kW. These properties give the radar a very high flexibility
of beam forming and beam steering. During the design phase of MAARSY several
model studies have been carried out in order to estimate the radiation pattern
for various combinations of beam forming and steering. However, parameters like
mutual coupling, active impedance and ground parameters may have an impact to
the radiation pattern, but hardly can be measured. Hence, experimental methods
need to be implied to verify the model results.
For
this purpose, the radar has occasionally been exclusively used in passive mode,
monitoring the noise power received from both distinct galactic noise sources
like e.g., Cassiopeia A and Cygnus A, and the complete diffuse galactic
background noise. The analysis of the collected dataset enables us to verify
beam forming and steering attempts. These results document the current status
of the radar during its development and provide valuable information for
further improvement. However, a limitation of these experiments is that they
provide information about the receiving system. The transmitting part of the
radar needs to be investigated separately by other means. For this purpose we
are planning an airborne electric field probe which shall be used to directly
sample the radiation pattern in the far field region.
Presented by: Renkwitz, Toralf
VHF
Radar Scatter Microstructure Measured by Combined Spatial and Frequency Domain
Interferometry: A developing approach
Jürgen
Röttger
Besides
the application of the Spatial Domain Interferometer method (SDI), measuring
particularly variations in the horizontal structure, also the Frequency Domain
Interferometry (FDI), measuring the line-of-site structure and velocity
(mostly vertical), had been introduced successfully. The combination of these
two methods, which is the main topic of this paper, allows determination of the
development of the three-dimensional fine structure of the atmospheric radar
refractivity. It will also be applied at high temporal resolution in the order
of several seconds, and it allows range resolutions down to better than 100 meters. These are observational requirements to view and
interpret the fine structure of atmospheric turbulence and stable laminae or
sheets, which are the generators of the refractive index irregularities giving rise
to VHF radar echoes.
This
novel way combining the Spatial and Frequency Domain Interferometry is called
in short “SFDI”, and measures the main three parameters of position, bulk and
fluctuating velocity of the refractivity distribution in three dimensions. The variation of these distribution functions show for instance
that the velocityfluctuations (usually assumed to be a measure of turbulence)
are not directly related to changes in radial position. The velocity
fluctuations can be interpreted as a measure of the roughness of moving,
specular reflecting, corrugated refractive index
surfaces and not necessarily as active turbulence. The consequences of these
and some more new observations using this technique will be discussed, namely
many MST VHF radar echoes are believed to bedue to specular-type reflections
from steep vertical gradients of the refractive index, which are corrugated or
rough.
This
roughness can be caused by a spectrum of waves and turbulence, which, however,
is not the particular scatterer itself. The view of locally rough surfaces of
refractivity with specular reflection regions moving with given velocities can
explain the shift and in particular the widening of the radar signal spectrum.
The latter is usually assumed to be a proper estimate of turbulence, which may
be questioned due to the shown specular-type reflection from quasi-horizontally
stratified rough layers. These implications will finally be discussed.
……………….
This
paper was originally presented at the International Symposium on the 25th
Anniversary of the MU Radar at RISH, Kyoto University, Uji, Japan, 2-3
September 2010.
Presented by: Röttger, Jürgen
Diurnal
wind variations in the lower-tropospheric wind over Japan as revealed with wind
profilers and analysis/reanalysis data sets
Takatoshi Sakazaki , Masatomo Fujiwara
Graduate School of Environmental Science, Hokkaido University
This
study investigates diurnal variations in lower-tropospheric wind (from surface
to 5 km in height) over Japan during 2002—2008 using data from 31 stations of
the Wind profiler Network and Data Acquisition System (WINDAS) as well as Japan
Meteorological Agency mesoscale analysis data (MANAL) and four global
reanalysis data sets (JRA25, ERA-Interim, NCEP1 and NCEP2). The diurnal and
semidiurnal components are extracted and analyzed to identify the dominant
dynamical processes.
An
analysis of wind profiler data shows that the characteristics of the diurnal
wind component heavily depend on height range and season. The maximum amplitude
of diurnal wind over Japan occurs in summer near the surface, in spring and
autumn at 1—3 km, and in winter at 3—5 km. Using analysis/reanalysis data, it
is found that these characteristics are found to be controlled by the four
different dynamical processes: (1) Local wind systems (e.g., land—sea breezes)
near the surface throughout the year, (2) Diurnal eastward-moving eddies at 1—3
km in winter-spring, (3) Medium-scale eastward travelling waves above 3 km, and
(4) Atmospheric tides above 3 km in summer.
On
the other hand, the semidiurnal wind component is primarily controlled by the
semidiurnal migrating tide above 1 km, and is influenced by local wind systems
below 1 km. The semidiurnal amplitude shows a marked seasonal variation with
its maximum in winter.
Presented by: Sakazaki, Takatoshi
Diurnal
wind variations in the upper-tropospheric and lower stratospheric wind over
Japan as revealed with MU radar and five reanalysis data sets
Takatoshi
Sakazaki 1, Masatomo Fujiwara 1, Hiroyuki Hashiguchi 2
1 Graduate School of Environmental Science, Hokkaido University
2 Research Institute for Sustainable Humanosphere, Kyoto University
Diurnal
variations in the troposphere are a source of the diurnal tides which are the
prevalent dynamical phenomenon in the mesosphere and lower thermosphere. They
are also discussed as contributing to the excitation of Rossby waves. Here we
study diurnal variations of upper tropospheric and lower stratospheric winds
(up to 22 km) over Japan from 1986 to 2008 mainly using data from the middle
and upper atmosphere (MU) radar (34.85°N, 136.10°E) and JRA25/JCDAS data, as
well as other four global reanalysis data sets (ERA40, ERA-Interim, NCEP1, and
NCEP2) and output data from Global Scale Wave Model (GSWM).
The
diurnal and semidiurnal components are extracted and analyzed. For the diurnal
wind component, the amplitude monotonically increases with height above 15–20
km. The phase shows an upward progression up to 15 to 20 km, while above 15 to
20 km, it shows a downward progression in most months.
It is found that the diurnal tide, defined as the diurnal component with
absolute zonal wave numbers of ≤6, is dominant in the upper troposphere
(explaining 60 to 80% of the variance) and in the stratosphere (explaining 80
to 90% of the variance). Also, medium-scale waves contributed to the diurnal
wind component in the upper troposphere from winter to spring (∼20% of the variance).
For
the semidiurnal wind component, the semidiurnal migrating tide is dominant
through the troposphere and the lower stratosphere. The amplitude shows a
marked seasonal variation in the troposphere being largest in winter and
smallest in summer.
Presented by: Sakazaki, Takatoshi
Preliminary
observation of temperature profiles by radio acoustic sounding system (RASS)
with a 1,280 MHz Lower Atmospheric Wind Profiler at Gadanki, India
T.V.
Chandrasekhar Sarma
1, Parvatala Srinivasulu 1, Toshitaka Tsuda 2
1 National Atmospheric Research Laboratory, Dept of Space, Govt of India,
Gadanki 517 112 AP, India
2 Research Institute for Sustainable Humanosphere, Kyoto University,
Uji, Kyoto 611 0011, Japan.
A
UHF wind profiler operating at 1280 MHz has been developed at NARL for
atmospheric studies in the planetary boundary layer. In order to explore
application of radio acoustic sounding system (RASS) technique to this
profiler, a suitable acoustic attachment was designed and implemented using
commercial-off-the-shelf (COTS) components. Preliminary experiments were
conducted on 27-30 August 2010 with this system along with the Indian MST-Radar
RASS system. Height profiles of virtual temperature, Tv,
in the planetary boundary layer were derived with 1µs and 0.25µs pulses,
corresponding to a height resolution of 150 m and about 40 m, respectively.
From the plot of Tv, Diurnal variation was
clearly recognized, and perturbations of Tv were also seen in
association with a precipitation event that occurred during this experiment.
The periodogram analysis of Tv profiles
shows that the maxima in the temperature occur around 1500 LT at lower heights
whereas they are progressively delayed as altitude increases. The amplitudes of
the diurnal temperature variation due to surface heating also decrease with
altitude. This phenomenon delineates the boundary layer from the free
troposphere. Using the Tv data the height
of the boundary layer could be clearly delineated. Usually the boundary layer
height extends up to about 3.5 km at Gadanki. However, as this preliminary experiment
was conducted on an overcast day, signatures of boundary layer height could be
discerned only up to the lower range bins of MST radar - RASS observations
viz., up to about 2.5 km. Simultaneous operations of the LAWP-RASS along with
the MST Radar-RASS and an onsite 50 m tower demonstrate the capability to
continuously profile the atmospheric temperature from near the ground to lower
stratosphere.
Presented by: Sarma, T.V.
Chandrasekhar
Semi-diurnal
tidal coupling at low-latitudes during sudden stratospheric warming events
S
Sridharan 1,
S Sathishkumar 2, S Gurubaran 2
1 National Atmospheric Research Laboratory, Gadanki 517 112, India
2 Indian Institute of Geomagnetism, EGRL, Krishnapuram, Tirunelveli
627 011, India
We
examined low-latitude mesospheric tidal variabilities in relation with the
occurrence of high-latitude sudden stratospheric warming (SSW) events. It is
found that there is an enhancement of semi-diurnal tide and suppression of
diurnal tide in the low-latitude mesosphere and consecutive occurrence of
counter-electrojet events lasting for several days. We proposed that the
enhancement of semi-diurnal tide may be due to the non-linear interaction
between migrating tides and planetary waves, the ozone variability due to
change in the circulation pattern in the middle atmosphere associated with the
SSW events and non-migrating tides generated by the latent heat released in the
deep equatorial convection induced by the potential vorticity advection at
higher levels as a result of breaking of Rossby waves during the SSW events.
While investigating which mechanism is more effective, it is found that the
ozone mixing ratio increases at low latitudes during the SSW and it could
probably be due to the SSW induced reversal of meridional circulation towards
southward, which may aid the transport of ozone from high to low latitudes, but
prevent the same from low to high latitudes. As semi-diurnal tide is produced
due to solar insolation absorption of ozone, the increase in the ozone mixing
ratio could be a reason for the increase in the semi-diurnal tidal amplitude.
The effectiveness of other suggested mechanisms has been investigated and the
results obtained will be presented during the meeting.
Presented by: Sathishkumar, S
The
program of the Antarctic Syowa MST/IS radar (PANSY)
Kaoru Sato 1, Masaki Tsutsumi 2, Toru Sato 3, Takuji Nakamura 2, Akinori Saito 4, Yoshihiro Tomikawa 2, Koji Nishimura 2, Hisao Yamagishi 2, Takashi Yamanouchi 2
1 Department of Earth and Planetary Science, The University of Tokyo
2 Naional Institute of Polar Research
3 Department of Communications and Computer Engineering, Kyoto
University
4 Department of Geophysics, Kyoto University
Since
2000, we have developed an MST/IS radar to be
operational in the Antarctic and have made feasibility studies. After solving
various significant problems such as treatment against strong winds, energy
saving, weight reduction, and efficient construction method, we reached the
final system design which is a VHF Doppler pulse radar with an active phased
array consisting of 1045 Yagis. This project was authorized as a main
observation plan for JARE (Japanese Antarctic Research Expedition) 52-57 in
2008, and finally funded by Japanese government in 2009. The radar construction
started in late December, 2010. Here we will present hot results from this
radar and discuss the uniqueness of the MST radar observation on the middle
atmosphere research. The observation will continue for 13 years covering one
solar cycle.
Presented by: Sato, Kaoru
Re-examination
of observed gravity wave characteristics by using a high-resolution GCM
Kaoru Sato
Department of Earth and Planetary Science, The
University of Tokyo
Gravity
waves are an essential component of the Earth's climate because of their
ability to transport momentum mainly upward from the lower atmosphere to the
middle atmosphere. The momentum deposition is important for maintaining weak
wind layers in the lower stratosphere and in the upper mesosphere, and for
simultaneously driving meridional circulations. The thermal structure of the
middle atmosphere is largely affected by adiabatic heating/cooling associated
with the wave-driven global circulations.
By
recent development of computer and satellite technologies, our knowledge on
global distribution and seasonal variation of small-scale fluctuations such as
gravity waves in the atmosphere has been significantly improved. For example,
it has been considered that gravity waves transport energy mainly vertically.
Thus, most gravity wave parameterizations used in the global circulation models
(GCM) ignore lateral propagation of gravity waves. However, recent results from
gravity-wave resolving GCM simulations and high-resolution satellite
observations indicate that lateral propagation of gravity waves even forced by
topography is not negligible and causes significant gravity wave drag over the
ocean. It was shown that an extra orographic gravity wave drag over 60S significantly
improved model simulation of seasonal variation of the stratospheric polar
vortex and hence the Antarctic ozone hole.
In
this talk, gravity wave characteristics such as seasonal variation of momentum
fluxes and wave energy and vertical wavenumber spectra shown by previous
studies using MST radars, radiosondes, and rockets are re-interpreted by
comparing with corresponding results from a high-resolution GCM.
Presented by: Sato, Kaoru
Atmospheric
processes and variability up to the lower thermosphere – Numerical studies with
HAMMONIA
Hauke
Schmidt
Max Planck Institute for Meteorology
Most
general circulation models of the middle atmosphere have their upper boundary
in the 70-90 km region while “classical” models of the thermosphere/ionosphere
mostly had their lower boundary near 80-95 km. HAMMONIA is one of the few
models built to overcome this separation. It is an upward extension of the
ECHAM5 general circulation model of MPI-M coupled to NCAR’s MOZAR3 chemistry
scheme. The model covers the atmospheric altitude range from the Earth's
surface up to 1.7*10-7 hPa (about 250 km), which means not only
tropo-, strato-, and mesosphere but also a considerable part of the
thermosphere. In the recent years HAMMONIA has been used for studies in a wide
range of fields, covering the effects of solar variability and GHG increase,
vertical coupling in the entire atmosphere, tidal activity, middle
atmospheric wave activity in general, long-periodic oscillations in the
mesosphere, and the distribution of trace gases. This presentation is intended
as an overview on results obtained with HAMMONIA. A focus will be on the region
of the mesosphere and lower thermosphere (MLT) which links the more dynamically
controlled lower and middle atmosphere with the upper atmosphere that is
influenced strongly by external forcing of in particular solar origin.
Consequently, in the MLT, it is often difficult to assess if signals are caused
by local processes (e.g. of varying absorption of solar radiation or changing
concentrations of radiatively active gases) or rather related to dynamical changes
in the lower atmosphere that are influencing the region due to changes in
propagation conditions of waves. It will be shown that numerical simulations
can provide a useful tool to better understand the possible role of these
different phenomena. Furthermore, the importance of observational studies for
numerical models like HAMMONIA and possible future improvements in entire
atmosphere modeling will be discussed.
Presented by: Schmidt, Hauke
Interferometric
measurements of meteor-head echoes with MAARSY
Carsten Schult , Gunter Stober , Ralph Latteck ,
Werner Singer , Markus Rapp
Institute of Atmospheric Physics (IAP)
Meteors
entering the Earth`s atmosphere typically ablate in an altitude range between
70-130 km. The kinetic energy of the meteoroid is sufficient to ionize the
meteoric constituents due to collisions with the neutral atmosphere which also
leads to the formation of a plasma surrounding the
meteoroid. This phenomenon is known as a meteor head echo and has recently been
studied with various high power large aperture (HPLA) radars.
Here
we present first meteor head echo observations with MAARSY (Middle Atmosphere
Alomar Radar System). The meteor head trajectories are determined by an
interferometric analysis using the multi-channel receiving capability of the
radar. Using this method we have studied the Geminid meteor shower during the
ECOMA sounding rocket campaign in 2010. These data are used to derive
distributions of entry velocities, source radiants and observation heights.
Presented by: Schult, Carsten
Diurnal
and Seasonal Variability of D-Region Electron Densities at 69°N
Werner
Singer 1, Martin Friedrich 2
1 Leibniz-Institute of
Atmospheric Physics (IAP) at the Rostock University, Kühlungsborn, Germany
2 Technical University of Graz, 8010 Graz, Austria
Electron
densities of the lower ionosphere are estimated with the Saura MF Doppler radar
(3.17 MHz) near Andenes, Norway since summer 2004. The narrow beam
transmitting/receiving antenna consists of 29 crossed half-wave dipoles
arranged as a Mills Cross resulting in a beam width of about 7°. Antenna and
transceiver system provide high flexibility in beam forming as well as the
capability forming beams with left and right circular polarization at alternate
pulses.
The
experiment utilizes partial reflections of ordinary and extraordinary component
waves from scatterers in the altitude range 50-90 km to estimate electron
number densities from differential absorption (DAE) and differential phase
(DPE) measurements. Height profiles are obtained between about 55 km and 90 km
with a time resolution of 9 minutes and a best height resolution of 1 km. The
electron density profiles independently derived from DAE and DPE measurements
are in remarkable good agreement. We discuss the diurnal and seasonal
variability of electron densities obtained at Andenes as well as the response
of D-region electron densities to solar activity storms, solar proton events,
and geomagnetic disturbances.
The
radar results are compared with previous rocket-borne radio wave propagation
measurements at Andenes as well as with recent co-located simultaneous insitu
observations using radio wave propagation experiments (differential absorption
and Faraday rotation) which showed good agreement between the two techniques.
In summer, the insitu measured electron densities show in presence of polar
mesosphere summer echoes (PMSE) an electron biteout at PMSE-altitudes. This
phenomenon is an often observed characteristic of the mesospheric electron
densities derive from the radar observations and confirmed by simultaneous
plasma probe measurements.
Presented by: Singer, Werner
Studying
mesospheric dynamics from PMSE backscatter using velocity azimuth displays
(VAD)
Gunter
Stober , Markus
Rapp , Ralph Latteck , Werner Singer , Marius Zecha
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
Since
several decades MST radars have been used to observe atmospheric dynamics.
These radars have been proven to provide reliable and continuous measurements
of prevailing winds and to gain information about the scattering processes from
the troposphere up to the mesosphere. The recently installed new MST radar
MAARSY at the island of Andoya in Northern Norway allows to
resolve the space time ambiguities due to its more advanced beam
steering capabilities, which permit to conduct systematic scanning experiments
at mesospheric altitudes with high spatial and temporal resolution. On the
basis of these experiments we applied a more advanced wind analysis technique,
such as a velocity azimuth display (VAD). The VAD method is suitable to
retrieve additional kinematic properties of the wind field, e.g. horizontal
divergence, stretching and shearing deformation. Here we present first results
applying the VAD technique to PMSE backscatter providing new insights into the
dynamical structure of the summer polar mesopause region.
Presented by: Stober, Gunter
In-situ
measurements of small-scale structures in neutrals and plasma species during
ECOMA-2010
Boris Strelnikov , Artur Szewczyk , Markus Rapp
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
In
December 2010 the fourth and final ECOMA rocket campaign was conducted at
Andøya Rocket Range (69 °N, 16 °E) in Northern Norway. Three sounding rockets
were launched to study the effect of the Geminid meteor shower on the
properties of meteor smoke particles. The main instrument, the ECOMA particle
detector has measured, among other things, number densities of charged dust
particles with very high spatial resolution. In addition, all payloads carried
instruments to measure densities of positive ions and neutral air also with
very high spatial resolution. These high resolution in-situ measurements allow
us to investigate small-scale features in all the constituents. In particular,
from the measured small-scale density fluctuations of neutral air we derive
turbulence energy dissipation rate. From the small-scale density fluctuations
of the charged species, i.e. meteoric smoke particles (MSP) and positive ions,
we derive the Schmidt number for the MSP and ions, respectively. We focus on
the last rocket flight, ECOMA09, where all the instruments produced the best
data.
Presented by: Strelnikov, Boris
Spectral
characteristics of incoherent scatter radar observations from the D-region
Irina Strelnikova
,
Markus Rapp
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
Radar
backscatter is a widely used powerful tool for studying the mesosphere. The two
main processes causing the backscattering of the radar waves from the D-region
plasma are the scattering from irregularities in electron density caused, for
example, by turbulence (coherent scatter) and "Thomson" scattering
from free electrons (incoherent scatter, IS).
We
present an IS data analysis technique that utilizes the shape of the spectra
(or, equivalently, the autocorrelation function) to infer information about
1)
the presence (or absence) of coherent structures in
the scattering volume, and 2) the presence of charged mesospheric aerosols
(only in the case of incoherent scatter).
This
technique has been applied to a total of 380 min of simultaneous and common
volume observations of PMSE with the EISCAT VHF and UHF radars in Tromsø
(Norway) made with a time resolution of 30 s.
We
considered both shape and width of the considered spectra and found that the
VHF spectra are on average well described by a Gauss shape, whereas the
UHF-spectra show a small deviation from this shape (due to relatively small
signal-to-noise ratios). Spectral widths do largely agree but show a small
systematic difference, i.e., the UHF spectra are on average 0.1 m/s narrower
than the VHF spectra at an average spectral width of 3.5 m/s. This small
systematic difference is largely explained by considering the overall effect of
beam-, shear-, and wave-broadening.
Finally,
results from the application of the same technique to coherent mesospheric
echoes from the winter mesosphere are also presented.
Presented by: Strelnikova, Irina
Long-term
variability of 16 day planetary wave in the equatorial mesosphere and lower
thermosphere in relation with QBO and SSW events
Sathishkumar
Sundararaman
1, Sridharan Sundarajan 2, Gurubaran Subaramanian 1, et al.
1 Indian Institute of Geomagnetism
2 National Atmospheric Research Laboratory
Planetary
waves with periods in the range of 2 to 16 days play an important role in the
dynamical coupling between the lower and middle atmosphere by transporting
energy and momentum both vertically and horizontally. As observations have
shown the inter-hemispheric propagation of 16 day planetary wave, in
particular, which becomes dominant during northern hemispheric winter, their
role in the lateral and vertical coupling needs to be addressed. It is commonly
observed as a wave of gravest symmetrical wavenumber 1 propagating westward. In
the present work the mesosphere and lower thermosphere (MLT) wind observations
from the medium frequency (MF) radar situated at Tirunelveli (8.7oN,
77.8oE) along with satellite and reanalysis data sets are used to
investigate the long term variability of ~16 day wave during 1993-2009 over
Tirunelveli. It is observed that the 16 day wave amplitude, as expected, shows
primary maximum in winter and secondary maximum in summer. Besides, the wave
activity appears to be enhanced in association with transition phase of quasi
biennial oscillation (QBO) and prior to the occurrence of sudden stratospheric
warming (SSW) events. The major SSW events of 2006 and 2009 appear to influence
the variabilities of the wave during winter, as the wave amplitudes decrease
drastically in the low-latitude mesosphere during and several days after the
occurrence of SSW events. More cases are being studied to establish the
relation between the variabilities of 16-day wave with QBO and SSW events and
their role in the variabilities of equatorial mesosphere, lower thermosphere
region. Results obtained will be presented during the meeting.
Presented by: Sundararaman,
Sathishkumar
De-noising
of atmospheric radar signals using Spectral based sub-space method
VN
Sureshbabu
1, VK Anandan 1, Toshitaka Tsuda 2, Jun-ichi Furumoto 2
1 ISTRAC, Indian Space Research Organisation, Bangalore -58, India
2 Research Institute for Sustainable Humanosphere (RISH), Kyoto
University, Uji, JAPAN
Post
beam steering (PBS) and digital beam forming (DBF) is getting greater interest
in radar signal processing community with its advantage in detecting the target
with better temporal and spatial resolution. This is supported by advanced
signal processing approaches and complex algorithms being developed in the
recent past with the availability of high power computers at a cheaper cost.
Generally
atmospheric signals are very weak and contaminated with noise. Retrieving the signal
information in the noise background is always an issue. Various techniques and
quality checks have been used to extract these signals. In this paper a study
has been carried out for de-noising the atmospheric signal using sub-space
based method on the data received from middle and upper atmospheric (MU) radar
at Shigaraki, Japan. MU radar is a monostatic pulsed phased array radar
operates at 46.5 MHz with a peak power of 1 MW. The array is configured as
circular array of 475 crossed Yagi elements which are grouped and formed by 25
different receiver channels for observational purpose The
array is also capable of steering the beam electronically using phase shifters
in transmit and receive path. The experiment was conducted with full array of
transmission (beam width 3.6o) in vertical direction. The data
collected is subjected to PBS using sub-space method mainly MUltiple SIgnal
Classification (MUSIC) and Eigen Value (EV) based method. The sub-space method
has unique advantage of looking distinctly on to signal sub-space and noise
sub-space for a given steered direction. Result shows that in the power
spectral distribution, the signals only visible by completely removing noise
fluctuations. This approach has shown distinct advantage in identifying the atmospheric
signals from a noisy environment. The wind velocity estimated through this
approach is compared with other estimation algorithms and shown excellent
agreement.
Presented by: Sureshbabu, VN
Coordinated
observations of mesospheric gravity waves with airglow imager, lidar, and radar
Shin
Suzuki 1, Takuji Nakamura 2, Matsumu K. Ejiri 2, Masaki Tsutsumi 1, Kazuo Shoikawa 1, Takuya D. Kawahara 3
1 Solar‐Terrestrial Environment Laboratory, Nagoya University,
Nagoya, Japan
2 National Institute of Polar Research, Tachikawa, Japan
3 Faculty of Engineering, Shinshu University, Nagano, Japan
To
investigate gravity wave dynamics in the mesosphere and lower thermosphere
(MLT) region, we conducted coordinated observations of mesospheric gravity
waves over Japan during the Aeronomy and Dynamics Observation campaign. Two all‐sky airglow imagers were used in
this campaign to derive a two‐dimensional structure of the gravity waves; these imagers
were installed at the middle and upper atmosphere (MU) observatory in Shigaraki
(34.9°N, 136.1°E) and at the Dynic Astropark Observatory in Taga (35.2°N,
136.3°E). Simultaneous measurements of the horizontal winds and the temperature
in the MLT region were provided by the meteor‐mode observations of the MU radar at
Shigaraki and by a sodium temperature lidar at Uji (34.9°N, 135.8°E),
respectively. On 2 October 2008, gravity waves having a horizontal wavelength
of ∼170 km, wave period of ∼1 h, and propagating northeastward
at ∼50 m/s were observed in the airglow
keograms. Similar wave structures were observed in the time series of the
meteor wind and lidar temperature data; the polarity of these waves varied
consistently with the airglow intensity variations according to the linear
theory of gravity waves. The phase speeds and momentum fluxes of the gravity
waves, estimated from the wind and temperature observations, were also in good
agreement with those obtained from the airglow measurements. These results
demonstrate, both qualitatively and quantitatively, that an identical gravity
wave structure was detected in all the airglow intensities, radar winds, and
lidar temperature.
Presented by: Suzuki, Shin
Comparison
of Calibrated Cn^2 Measurements and Determination of Kinetic Energy Dissipation
Rates from a Relatively High-Density VHF Windprofiler Network in Canada
N. Swarnalingam1 and W.
K. Hocking2
(1) MYU Consulting, London, Ontario,
Canada.
(2) Department of Physics and
Astronomy, University of Western Ontario, London, Ontario, Canada.
The
O-Q NET is a network of relatively closely spaced VHF windprofiler radars in
Ontario and Quebec, Canada. Using frequencies in the range 40 to 55 MHz, the
network provides hourly horizontal winds, vertical winds, turbulence estimates,
tropopause height determination, and scatterer anisotropy characteristics, from
400 m to typically 14 km altitude. The radars are absolutely calibrated and
their efficiencies are determined using the method described in Swarnalingam et. al., 2009. This allows direct measurements
of refractive index structure function constant Cn^2 In
this paper, we compare Cn^2 measurements and determine the kinetic energy
dissipation rates using on site in-situ measurements.
Presented by: Swarnalingam,
Nimalan
EISCAT-3D:
Volumetric imaging radar in Northern Scandinavia for studies of the atmospheric
and geospace environment
Esa Turunen , et al.
EISCAT Scientific Association, Kiruna, Sweden
EISCAT_3D
will be the next-generation incoherent scatter radar (ISR) for the study of the
atmosphere and geospace environment. It will be a distributed phased-array
facility built in modular fashion from a few tens of thousands up to 100 000
individual antenna elements, located in northern Scandinavia in the auroral
zone and at the edge of the polar vortex. The first Design Study of the
technical concept was conducted in 2005-2009. As the EISCAT_3D proposal was
accepted on the European Roadmap of strategically important large-scale
research infrastructures, the EU granted funding of 4.5 MEUR for a 4-year long
Preparatory Phase study in 2010-2014. Recently the Swedish Research Council
granted a 0.8 MEUR planning support for the next 2 years in order to facilitate
the technical development so, that construction could start as soon as funding
is available.
EISCAT_3D
will go beyond anything currently available in ISR technology, with multiple
large phased-array antenna transmitters/receivers and multiple receiver sites,
direct-sampling receivers and digital beam-forming and beam-steering. Five key
attributes are combined in one radar: (1) volumetric imaging and tracking in a
large geographic area, (2) aperture synthesis imaging for small scale
structures down to metres, (3) multistatic configuration for calculation of
vector velocities in the atmosphere as well as for using adaptive Faraday
rotation techniques, (4) by an order-of-magnitude improvement in sensitivity
and (5) transmitter flexibility allowing arbitrary modulations.
In
addition to standard remote sensing of the ionospheric plasma, EISCAT_3D
addresses the interactions between geospace and the atmosphere, as well as
between the atmospheric layers themselves and offers a unique opportunity to
study the atmospheric energy budget and solar system influences, such as the
effects of solar wind, meteors, dust, energetic particles and cosmic rays in
the atmosphere. New measurements will support studies of upward energy flow
from the stratosphere, to the mesosphere, and thermosphere, lower atmospheric
tidal variability and interactions with the mean atmospheric circulation,
gravity waves, planetary waves, and ionospheric variations, gravity wave
excitation mechanisms, the implications of significant observed gravity wave
geographical and temporal variability, and the impacts of stratospheric warming
events on the ionosphere.
In
this talk, after first reviewing the science case and concept proposed in the
Design Study, we summarize the current development of the technical work, as
well as the major results after the first year of the Preparatory Phase,
including the proposed site configuration, technical performance target and
signal processing.
Presented by: Turunen, Esa
Sodankylä-Leicester
Ionospheric Coupling Experiment - Selected First Results
Thomas
Ulich 1, Juha Vierinen 1, Neil Arnold 2, Chris Thomas 2, Mark Lester 2
1 Sodankylä Geophysical Observatory, Finland
2 Leicester University, U.K.
The
Dept of Physics and Astronomy, Leicester University, has installed a new
SKiYMET Meteor Radar at the Sodankylä Geophysical Observatory (SGO), Sodankylä,
Northern Finland (67° 22' N, 26° 38' E). SGO operates the radar as part of the
joint research endeavour SLICE (Sodankylä-Leicester Ionospheric Coupling
Experiment).
The
radar has seven crossed dipole aerials in a cross configuration (14 receiver
channels) and one crossed dipole transmitter antenna. It operates currently at
15kW power and the centre frequency is 36.9 MHz. Operations began in early
December
2008.
Here
we will present selected first results, most notably
we will show mesurements during Sudden Statospheric Warming (SSW) events. We
invite colleagues interested in the data to get in touch with us
(thomas.ulich@sgo.fi).
Presented by: Ulich, Thomas
The
transceiver-based approach to phased array radars – applications and advantages
Brenton Vandepeer , Pramod Aryal , Adrian Murphy ,
Daniel O'Connor , Brian Fuller
Genesis Software Pty Ltd, Adelaide, Australia
Newly-developed
transceiver modules for high power pulsed coherent radars find application in
MST, meteor, ionospheric and boundary layer troposphere radar topologies. The
transceiver approach breaks the shackles usually encountered in traditional
designs, allowing increased freedom in the design of antenna arrays, steered
beam experiments, and other novel radiation pattern shapes. We discuss a number
of examples where the use of transceiver modules as the core building block of
the radar system can yield these advantages, and where increased precision in
beam forming results when contrasted to traditional approaches.
Presented by: Vandepeer, Brenton
Quasi-coherent
bistatic radar - implementation and observations
Brenton Vandepeer , Adrian Murphy , Daniel O'Connor ,
Brian Fuller
Genesis Software Pty Ltd, Adelaide, Australia
A
technique for operating two or more non-colocated coherent radars is presented
in which both pulse timing and carrier frequency are synchronised. This allows
accurate and reliable Doppler measurements to be made of targets in the common
observable volume using forward scattered radiation. The technique has been
utilised to build variations of SKiYMET meteor radars which are able to detect
and map forward scattered echoes from meteor trails in the mesosphere and lower
thermosphere. Further applications include bistatic receive stations for MST,
boundary layer troposphere and ionospheric radars. Components of these radar
systems are discussed to exemplify the technique and some observations
presented.
Presented by: Vandepeer, Brenton
Colorado
Software Defined Radar: Hardware, Results, Reconfigurabity and Deployment
Cody Vaudrin , Scott Palo
University of Colorado
An
overview and hardware update of the Colorado Software Defined Radar (CoSRad)
system. A brief hardware examination is followed by a description and
demonstration of the time coherent echo detection software and visualization
tools using data recently acquired at Platteville, Colorado and at the
Jicamarca Radio Observatory. An educational slide on the roll of noise and
interference in direct-convert sampling systems is followed by the presentation
of a number of interesting and unusual echoes extracted from a variety of data
sets.
CoSRad’s
reconfigurability is showcased through a description of current and past
experiments with a variety of existing radar systems including those located at
Jicamarca, Platteville, Argentina and the South Pole. A NOAA funded Linear
Frequency Modulation Continuous Wave (LFMCW) Tropospheric Boundary Layer Radar
based on CoSRad currently in development is discussed. Geographically
distributed synchronization of multiple receivers is mentioned. Our talk
concludes with various logistical elements and anecdotes including cost and the
challenges involved with deploying hardware in hostile international
environments.An overview and hardware update of the Colorado Software Defined
Radar (CoSRad) system. A brief hardware examination is followed by a
description and demonstration of the time coherent echo detection software and
visualization tools using data recently acquired at Platteville, Colorado and
at the Jicamarca Radio Observatory. An educational slide on the roll of noise
and interference in direct-convert sampling systems is followed by the
presentation of a number of interesting and unusual echoes extracted from a
variety of data sets.
Presented by: Vaudrin, Cody
Frequency
dependence of gravity wave momentum flux estimates in the lower atmosphere:
First observations using MST radar wind data at Gadanki
P Vinay
Kumar 1, M.C. Ajay Kumar 2, P. V. Rao 3, Salauddin Mohammad 1, Gopa Dutta 1
1 Vignana Bharathi Institute of Technology, Aushapur, Hyderabad,
India.
2 Vanjari Seethaiah Memorial College of Engg.,
Patancheru, Hyderabad, India.
3 Vasavi College of Engineering,
Ibrahimbagh, Hyderabad, India.
It
is now well established that internal gravity waves play a significant role in
the momentum budget and thermal structure of the lower and middle atmosphere.
The gravity wave parameterization problem is one of the most significant issue
confronting climate modelers. MST radar is a powerful tool to measure momentum
flux of gravity waves. This paper addresses the important issue of comparison
of momentum fluxes carried by gravity waves in two period bands - (2-8) hours
and Inertia Gravity Wave (IGW) using Gadanki MST radar data, a tropical Indian
station in the northern hemisphere. It is found that gravity waves of 2-8 hour
periodicity transport higher momentum flux than IGW in the troposphere and lower
stratosphere. Momentum flux frequency spectra show prominent oscillations
between 2.5 - 6 hours. Wavelet transforms show significant variability and
localization of the estimates with time. The dominant gravity wave momentum
fluxes are found to arise from discrete and localized wave packets in frequency
and time.
Presented by: Vinay Kumar, P
Small
scale turbulence and instabilities observed simultaneously by radiosondes and
the MU radar
Richard
Wilson 1, Hubert Luce 2, Hiroyuki Hashiguchi 3, Francis Dalaudier 1, Shoichiro Fukao 4, Tomoyuki Nakajo 4, Yoshiaki Shibagaki 5, Masanori Yabuki 3, Jun-ichi Furumoto 3
1 LATMOS-IPSL, UPMC Univ Paris 06, Univ. Versailles St-Quentin,
CNRS/INSU, Paris, France
2 Université du Sud- Toulon Var, La Garde, France
3 Research Institute for Sustainable Humanosphere, Kyoto University,
Uji, Japan
4 Department of Electrical, Electronics and Computer Engineering,
Fukui University of Technology, Fukui, Japan
5 Osaka Electro-Communication University, Neyagawa, Japan
A
Japanese-French field campaign devoted to the study of turbulence and
instabilities in the troposphere and lower stratosphere was conducted in
September 2011 for three weeks at the Shigaraki MU observatory (Japan). During
the experiment, 59 radiosondes (Vaisala RS92G) were successfully launched and
MU radar/lidar measurements were performed.
The
detection of turbulence from the in situ profiles is based on a Thorpe
analysis. We have developed an original method for selecting the "true"
turbulent events within the profile, i.e for rejecting the events induced by
instrumental noise. The method is based on both an optimal noise reduction and
a statistical hypothesis test.
From
the raw data of radiosoundings (3-6 m vertical resolution), we detected those
turbulent regions whose vertical extent is larger than ~ 40 m in the
troposphere, ~15 m in the lower stratosphere. By taking into account the water
vapor saturation effects, we also detected (conditional) static instabilities
within the clouds.
In
addition, the MU radar measurements were acquired in range imaging (FII) mode,
allowing to observe turbulence and KH instabilities with an exceptional
time-space resolution (~ several 10 m, 20 s).
We
shall present the very first results of this campaign including direct
comparisons of turbulent events observed simultaneously by radiosondes and MU
radar.
Presented by: Wilson, Richard
Air
quality measurements with Lidar, SODAR and tethered balloon profiling in the
surface boundary layer over Shigaraki, Japan
Masanori
Yabuki 1, Kenshi Takahashi 1, Taichi Hayashi 2, Chikara Miyawaki 1, Makoto Matsuda 1, Toshitaka Tsuda 1
1 Research Institute for Sustainable Humanosphere, Kyoto University,
Kyoto, Japan
2 Disaster Prevention Research Institute, Kyoto, Japan
Knowledge
of the properties of atmospheric minor constituents that determines air quality
is essential for studies on climate change and its effects on human health. The
concentrations of ambient trace gases and aerosols, which are emitted by
natural and anthropogenic sources, are influenced by the diffusion due to the
thermodynamic processes during the air-mass transportation along the prevailing
wind flow. On the other hand, their chemical and physical properties vary both
temporally and spatially in the course of different atmospheric processes such
as scavenging, nucleation, evaporation and condensation. Therefore, to gain an
understanding of the air quality, a comprehensive approach that takes into consideration
atmospheric chemistry as well as dynamics and thermodynamics has to be adopted.
Here, we focus on the vertical distributions of trace gases and aerosols in the
surface boundary layer and their variation with wind velocity and water vapor
content. For this purpose, simultaneous measurements with lidar, SODAR and
tethered balloon profiling were carried out at a middle and upper atmosphere
(MU) radar site (34.9 ° N, 136.1 ° E), Shigaraki, Japan, on September 5–16,
2011. Water vapor mixing ratio and aerosol properties were determined using a
multi-wavelength Mie-Raman lidar designed for performing measurements from near
the surface. Aerosol characteristics such as particle size, shape, and
hygroscopicity can be estimated from this lidar data. The SODAR was used for
observing the wind velocity at altitudes from 50 to 400 m. Measurements with a
high temporal resolution were made for profiling trace gases by using a
tethered balloon as a research platform and instruments for real-time gas
analysis. We also observed the altitude dependence of the secondary species
such as nanoparticles that are formed from NOx, SO2, volatile organic
components (VOCs), etc. via atmospheric photochemical reactions. In this study,
we introduce an outline of our research on measurement of trace gases and
aerosols. We also show the preliminary results related to the altitude variance
of the atmospheric minor constituents with the vertical flow.
Presented by: Yabuki, Masanori
Measurement
of vertical air velocity and hydrometeor in stratiform precipitation by the
Equatorial Atmosphere Radar and polarization lidar
Masayuki
K. Yamamoto
1, Tomoaki Mega 1, Yasukuni Shibata 2, Makoto Abo 2, Hiroyuki Hashiguchi 1, Toyoshi Shimomai 3, Yoshiaki Shibagaki 4, Noriyuki Nishi 5, Mamoru Yamamoto 1, Manabu D. Yamanaka 6, Shoichiro Fukao 7, Timbul Manik 8
1 Research Institute for Sustainable Humanosphere, Kyoto University
2 Faculty of System Design, Tokyo Metropolitan University
3 Interdisciplinary Faculty of Science and Engineering, Shimane
University
4 Faculty of Information and Communication Engineering, Osaka
Electro-Communication University
5 Graduate School of Science, Kyoto University
6 Japan Agency for Marine-Earth Science and Technology,
SATREPS-MCCOE Promotion Office, Kobe University
7 Fukui University of Technology
8 National Institute of Aeronautics and Space (LAPAN), Indonesia
Simultaneous
measurement of vertical air velocity (W), particle fall velocity, and
hydrometeor phase was carried out using a 47-MHz wind profiling radar and a
polarization lidar installed at Sumatra, Indonesia (0.2S, 100.32E, 865 m MSL)
in December 2008. The 47-MHz wind profiling radar, referred to as the
Equatorial Atmosphere Radar (EAR), measured W and reflectivity-weighted
particle fall velocity relative to the air (Vz) simultaneously. The
lidar measured linear depolization ratio (LDR), which is an indicator of
hydrometeor sphericity. A stratiform precipitation case on 8 December 2008 and
that on 16 December 2008 were compared to describe differences of W, Vz,
and LDR.
Surface
rainfall intensity was greater than 2 mm/h in the 16 December case, while
raindrops evaporated until they reached to the ground in the 8 December case.
Upward W above the melting level was greater than 0.2 m/s in the 16 December
case, while it was weak (less than 0.1 m/s) or absent in the 8 December case. Vz
of 1.6 m/s at 300 m above the 0 degC altitude (5.2 km MSL) in the 16 December
case was greater than the 8 December case (1.3 m/s). The thickness of melting
layer in the 16 December case (900 m) was greater than the 8 December case (300
m). Because Vz is an indicator of particle size, the results
suggests that the size growth of hydrometeors under the presence of upward W
contributed to the formation of thicker melting layer in the 16 December case.
Owing to complex interfaces of water-coated ice crystal branches, LDR at the
melting level increased 0.17- 0.20 in the two cases. Lidar dark band was also
observed in the two cases.
Vz
of raindrops in the 16 December case (7.0-7.5 m/s) was greater than that in the
8 December case (3.7-3.9 m/s) due to larger sized raindrops in the 16 December
case. LDR of raindrops in the 8 December case was less than 0.01, while it was
0.05-0.10 in the 16 December case. A possible reason for the LDR difference is
discussed.
Presented
by: Yamamoto, Masayuki K.
Development
of digital radar receiver using software-defined radio technique
Masayuki
K. Yamamoto ,
Hiroyuki Hashiguchi , Noor Hafizah Binti Abdul Aziz , Youhei Wakisaka , Mamoru
Yamamoto
Research Institute for Sustainable Humanosphere (RISH), Kyoto University
Coherent
radar imaging (CRI) is important to clarify fine-scale structure of turbulence,
quantitative measurement of turbulence parameters, and clutter rejection. In
order to implement CRI function to conventional atmospheric radars with reduced
development cost, RISH has been developing new digital receiver system. As the
computer-hosted hardware, Universal Software Radio Peripheral 2 (USRP2) offered
by Ettus Research LLC is used. USRP2 is connected to the host computer through
Gigabit Ethernet interface. The host computer uses GNU Radio and Universal
Hardware Driver (UHD) software libraries for controlling USRP2. Because only
sequential data transfer is available, the host computer executes ranging by
detecting transmitted signals leaked to the receiving line. On-line data signal
processing (i.e., pulse decoding and coherent integration) is also executed by
the host computer. Current receiver system configuration and measurement
results using a 1.3-GHz wind profiling radar are presented.
Presented
by: Yamamoto, Masayuki K.
Observation
of turbulence and clouds in the tropics by the Equatorial Atmosphere Radar
Masayuki
K. Yamamoto
1, Hiroyuki Hashiguchi 1, Mamoru Yamamoto 1, Shoichiro Fukao 2
1 Research Institute for Sustainable Humanosphere, Kyoto University
2 Fukui University of Technology
Since its installation at the
Equatorial Atmosphere Observatory at Sumatra, Indonesia (0.2S, 100.32E) in
2001, the Equatorial Atmosphere Radar (EAR), a 47-MHz
atmospheric radar, has been utilized for studies of turbulence and clouds in
the tropics.
Owing
to its output power of 100 kW and active phased array antenna with a diameter
of approximately 110 m, the EAR is able to measure wind and turbulence up to an
altitude of approximately 20 km. EAR observations have revealed turbulence
generation associated with breaking of Kelvin wave and easterly wind jet in the
upper troposphere-lower stratosphere (UTLS) region. Range imaging (RIM) is a
technique which improves radar range resolution by applying adaptive signal
processing to signals collected using multiple carrier frequencies. RIM
measurement using the EAR has revealed fine-scale structure of turbulence
associated with breaking of Kelvin wave in the UTLS region. In the
presentation, results of wave and turbulence measurements by the EAR are
reviewed.
Vertical
wind is a crucial factor that determines generation and dissipation of clouds.
The EAR is able to measure vertical wind velocity both in clear and cloud
regions, because atmospheric radars using approximately 50-MHz frequency are
able to detect echoes from refractive index irregularities at Bragg scale and
those from hydrometeors separately. On the other hand, millimeter-wave cloud
radars and lidars are useful to measure cloud particles. Therefore
multi-instrument measurements using the EAR and cloud radar/lidar have been
carried out in order to observe interactions between vertical wind and cloud
processes. In the presentation, results from multi-instrument measurement of
cloud and precipitation using the EAR are reviewed.
Presented
by: Yamamoto, Masayuki K.
HCOPAR:
Hainan VHF Coherent Scatter Phased Array Radar System Description and First
Results
Jingye Yan 1, Jürgen Röttger, Sheping Shang 1, Jiankui Shi 1, Heguang Liu 1, Chi Wang 1, Ji Wu 1
1 National Space Science Center, Chinese Academy of Sciences.
Hainan
VHF Coherent Scatter Phased Array Radar (HCOPAR) is a key equipment of the
Chinese Meridian Space Weather Monitoring Project (Meridian Project for
short). The project set up a large-scale ground-based monitoring system
composed of 15 stations along the longitude of 120°E and the latitude of
30°N. After 3 years of constructing, 95 equipments have been built. Among
them the HCOPAR and a few other equipments are located at Hainan Sounding Rocket
Base (HSRB, 19.31N,109.08E), Chinese Academy of
Sciences. |
HCOPAR
is implemented with active phase array and is composed of 72 Yagi antennas. Its
array is a rectangle of 4 by 18 elements. With 0.7 lambda distance between
adjacent elements, the radar provides a scanning field of -30º~+30º,the antenna beam width is of 5ºand 21º along latitude and
longitude, respectively. Differing from similar equipments in the world, HCOPAR
is benefited from the advances of modern electricity. Dedicated pre-processor is
designed and imbedded into each T/R unit. The pre-processor is composed of high
speed DSP and FPGA. It receives synchronous clock from the central high
performance crystal oscillator to keep all the array work with accurate timing.
The pre-processor communicates with the hiberarchy central processors via
TCP/IP protocol. Bidirectional signals flow through the star-shape network
cables between central processor and all the pre-processors. The transmitted
waveform, coding method, signal processing and many other parameters are
reconfigurable even for single element. The transmitting signal is generated at
local T/R unit with direct digital synthesizer (DDS). Received echo is
digitized at local T/R unit and transferred to central computer over TCP/IP.
Amplitude and phase weighting over the array is applicable. Basically, HCOPAR
is a combination of 72 small radars. Each is reconfigurable and works
independently/synchronously, according to user’s requirements.
The
quality of the raw data has shown to be of good standard. It is already allows
some initial interpretation in terms of the scattering structure of
irregularities. This can be deduced from the variation of signal power as
function of beaming angle, which primarily is dominated by the aspect
sensitivity of the scatterers. The variability of power spectra indicates
mostly type 2 irregularities as typically seen in the Equatorial Electrojet
(EEJ).
It will be briefly discussed how spatial interferometer measurements should be
done as a next obvious step in the application of this radar.
Presented by: Yan, Jingye
Occurrence
of mid-latitude field-aligned irregularities observed with VHF coherent scatter
ionospheric radar in South Korea
Tae-Yong
Yang 1, Young-Sil Kwak 2, Jae-Jin Lee 2, Young-Deuk Park 2
1 Korea Astronomy and Space Science Institute / University of
Science and Technology
2 Korea Astronomy and Space Science Institute
The
40.8-MHz VHF coherent scatter ionospheric radar, located in South
Korea(Gyeryong, 36.18°N, 127.14°E), has been operating since December 2009 to
investigate ionosphere E- and F-region field-aligned irregularities(FAIs) of
mid-latitude. During the observation, we found E- and F-region FAIs appeared
frequently: interesting daytime irregularities, continuous echoes during the post-sunrise
period and Quasi-Periodic(QP) echoes at nighttime for
E region; strong post-sunset and pre-sunrise FAIs for F region. We present
characteristics of mid-latitude E- and F-region plasma irregularities observed
using Korea VHF radar. Additionally, we also present seasonal and local time
variations of occurrence of mid-latitude E- and F-region FAIs during low solar
activity period, December 2009 - May 2011. It is worth to note our occurrence
result since long term observation over a year in the mid-latitude has not yet
been carried out.
Presented by: Yang, Tae-Yong
A Low
Power Software Defined Incoherent Scatter Radar System Design Concept for
Continuous Sounding the Earth's Ionosphere
Ming Yao
Nanchang University, Nanchang, China
The
incoherent scatter radar (ISR) is the only ground based instrument, which can
detect the space plasma parameters from tens to thousands of kilometers height
above the earth, especially the ionosphere. Although ISR is the most effective
ionospheric sounding instrument, its’ exorbitant constructing and running fee
limit its wide application. Compared with the traditional ISR, the novel ISR
design concept introduced in this paper has the advantages of low power and
continuous working. It can probe real time plasma parameters in the whole
ionosphere range (80-1000 Km). Successful development of such ISR will resolve
the problem of continuous detection of ionospheric electric field and other
parameters. This paper will introduce the design concept of this low power
software defined ISR.
Presented by: Yao, Ming
Atmospheric
Density and the Height Distribution of Meteor Radar Detections
Joel
Younger 1, Iain Reid 1, Robert Vincent 1, Damian Murphy 2
1 University of Adelaide
2 Australian Antarctic Division
Radar-detectable
meteor trails are formed at heights around 70-110 km by the ionization of
material evaporated from the surface of meteoroids entering the atmosphere. The
height at which meteor trails occur is a function of the properties of the
incident meteoroids and the density profile of the atmosphere. Variations in
the density profile of the atmosphere will cause variations in the distribution
of heights over which meteors are detected.
The
formation of meteor trails for a population of meteoroids with different
initial sizes, velocities, and angles-of-entry have been numerically simulated
using model atmospheric data. The meteor radar response function was then
applied to the simulated trails to determine whether each trail was detected.
The detected trails were then weighted according to the properties of the
simulated meteor population to produce a height distribution of detected
meteors. It is predicted that the width of the approximately Gaussian height
distribution of meteor detections is a nearly linear function of the density
scale height of the atmosphere. This result can be derived independently from
an analytic consideration of the energy budget of individual meteors during
ablation. Further predictions include a correlation between the peak detection
height and extinction height (minimum detected height) and the height of
constant density surfaces in the meteor ablation region. A comparison of model
atmospheric density profiles with actual meteor detections is consistent with
these predictions. As such, the height distribution of meteor radar detections
may provide a method for observing density variations in the meteor ablation
region.
Presented by: Younger, Joel
The
Effect of Aerosol Absorption on Meteor Decay Times at Different Wavelengths
Joel
Younger 1, Iain Reid 1, Robert Vincent 1, Damian Murphy 2
1 University of Adelaide
2 Australian Antarctic Division
The
free electrons in meteoric plasma are susceptible to absorption by aerosols in
the meteor ablation region. The loss of electrons from meteor trails due to
absorption by aerosols may be responsible for the discrepancy in echo decay
time estimates of the ambipolar diffusion coefficient made by meteor radars
with different wavelengths.
It
is possible to numerically simulate the simultaneous diffusion and absorption
of meteor trail electrons to determine the effect of aerosol absorption on the
decay time of meteors with different initial electron line densities measured
with different radar wavelengths. The simulations performed indicate that the
observed decay time of a meteor radar echo in an absorptive environment may be
reduced or extended, depending on the initial line density of the trail and the
properties of the absorbing aerosols. The dependence of the decay time
modification on the properties of the absorbing aerosols provides an
opportunity to determine under what aerosol regimes absorption becomes a
significant factor in the estimation of the ambipolar diffusion coefficient
from meteor radar echo decay times.
The
results of the numerical simulations have been compared with observations of
co-located 33 and 55 MHz meteor radars located at Davis Station, Antarctica. A
comparison of the disagreement in diffusion coefficients as a function of
electron line density is consistent with the predictions of the numerical
simulations. Expected seasonal trends due to the modulation of aerosol charge
by solar irradiance and the formation of PMSE are, however, not seen, which may
indicate that aerosol absorption is not the sole cause of the wavelength
dependence of meteor radar diffusion coefficient estimates.
Presented by: Younger, Joel
The
Diffusion of Multiple Ionic Species in Meteor Trails
Joel Younger , Iain Reid , Robert Vincent
University of Adelaide
Meteor
trails are composed of material evaporated from the surface of ablating
meteoroids and can be comprised of a number of different elements. The
diffusion of ions in meteor trails is usually considered using an average value
for all of the elements in the trail. Numerical simulations have been performed
to determine the diffusive behavior of meteor trails made out of
multi-constituent plasma. This is further separated into two problems: that of
the initial radius of the distributions of different ions and the subsequent
diffusion of different ions in a meteor trail. Particular attention is paid to
the effect of multi-species diffusion on the observed meteor echo decay times
at different radar wavelengths.
Presented by: Younger, Joel
Accuracy
of Meteor Shower Velocity Estimates Obtained from the Fresnel Transform Method
Joel
Younger 1, Iain Reid 1, Robert Vincent 1, Damian Murphy 2
1 University of Adelaide
2 Australian Antarctic Division
Dedicated
meteor radar systems can be used to detect meteor showers caused by discrete
filaments of debris in Earth-intersecting orbits. The velocities of individual
candidate meteors for each shower can be used to produce an estimate of the
apparent geocentric velocity of meteoroids in the shower. A meteor shower is
formed by bodies with the same orbital parameters, which means that all
meteoroids in a shower share the same initial velocity. Therefore, an analysis
of the distribution of velocities of shower meteors can also be used to assess
the precision of the velocity estimation technique. Furthermore, the
observations of the same meteor showers made by other radar techniques and
optical methods provide an opportunity to compare the accuracy of shower velocity
estimates.
The
velocity estimates of 522 shower detections obtained during a survey of VHF
meteor radar data from 2006-2007 have been used to assess the performance of
the Fresnel transform method of velocity estimation. It is shown that the
estimates for high velocity showers above at least 50 km/s are strongly
influenced by the angle-of-entry of the meteors, due to the removal of
early-stage ablation meteors in shallow trajectories by the underdense echo
high altitude cutoff phenomena. Furthermore, it is shown that the precision of
single-station estimates of meteor shower velocity is strongly dependent on the
number of shower meteors detected, converging to a relative value of about 8%
for intense showers.
Presented by: Younger, Joel
The
Role of Sputtering in the Formation of Meteor Trails
Joel Younger , Iain Reid , Robert Vincent
University of Adelaide
Sputtering
of material from the surface of meteoroids can occur when collisions with
molecules of atmospheric gasses impart energy in excess of the lattice energy
of the meteoric material. While most of the detectable plasma in meteor trails
is produced by evaporation at high temperatures, sputtering produces mass loss
at high altitudes well in advance of the onset of evaporation. Numerical
simulations have been performed for meteoroids with different compositions,
initial sizes, and initial velocities. It was found that sputtering only
constitutes 1-2% of the detectable ionization in underdense meteor trails. This
result allows the ablation of meteoroids to be modeled using the simpler all
thermal energy budget equation. It was however found that sputtering can
produce ionization at much higher altitudes than is seen for the case of
evaporation only. This indicates that sputtering may be an important mass loss
mechanism for high altitude meteors as detected by radars with longer
wavelengths.
Presented by: Younger, Joel
3D-measurement
results by MAARSY using radar interferometry methods
Marius
Zecha , Ralph
Latteck , Markus Rapp , Werner Singer , Gunter Stober , Toralf Renkwitz
Leibniz-Institute of Atmospheric Physics (IAP) at the Rostock University,
Kühlungsborn, Germany
Usually
the spatial resolution of measurements by pulsed VHF radars is limited by the
radar beam width, transmitting pulse length, and sampling time. Due to these
technical restrictions the typical small-scale structures in the mesosphere
often cannot be resolved. Furthermore the quality of the estimation of dynamic
atmosphere parameters is reduced if the position and direction of scatter
returns cannot determined exactly.
Radar
interferometry methods have been developed to reduce these limitations
In
the recent years the MST radar MAARSY was installed in Andenes/Norway (69°N).
This new radar was designed to allow improved three-dimensional observations in
the atmosphere. It consists of 433 Yagis and allows a minimum beam width of
about 4 degree. The beam direction can be changed pulse-by-pulse freely in
azimuth angle and practicable up to 40 degree in zenith angle. The typical used
pulse length is set to 300 m and could be reduced down to 50 m. Up to 16
receiving channels of spaced antennas can be used.
In
this presentation we demonstrate the detection of the angle-of-arrival and the verification
of the beam steering with MAARSY. We show the improvement of measurement
results by using radar interferometry methods. The differences to the results
of conventional methods depend on beam width, range resolution, distance
between radar and measurement volume, zenith angle of the beam, and so on. We
show that the application of interferometry is necessary to improve
considerably the quality of 3D-measurement results.
Presented by: Zecha, Marius