17:35 - 17:35
Effect of cyclone Nilofar on mesospheric wave dynamics as inferred from optical nightglow observations from Mt. Abu, India
Ravindra Pratap Singh1, 2, Duggirala Pallamraju1
1Space and Atmospheric Sciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, India
2Department of Physics, Sardar Patel University, Vallabh Vidyanagar, India

Mesospheric nightglow intensities at three emissions (O2(0-1), OH(6-2) bands, and Na(589.3 nm)) from a low-latitude location, Gurushikhar, Mount Abu (24.60N, 72.80E), in India, showed similar wave features on 26 October 2014 with a common periodicity of around 4-hours. A convective activity due to the cyclone Nilofar, which had developed in the Arabian Sea during 25-31 October 2014, was found to be the source as this too showed a gravity wave period coherent with that of the mesospheric emissions on the 26th. The periodicities at the source region were obtained using Outgoing Longwave Radiation (OLR) fluxes (derived from Kalpana-1 satellite) which were used as a tracer of tropospheric activity. The observed downward phase propagation in the intensity fluctuations of the nightglow emissions confirms that the gravity wave travelled upwards and from the phase offset in time between the residuals of O2 and OH emission intensities and the observed common periodicity the vertical phase speed and vertical wavelength have been found to be 1.13 ms-1 and 16.47 km. From the wavelet analyses it is seen that the travel time of the wave from the convection region to O2 emission height was around 8.1 hours. From these observations, the horizontal phase speed and horizontal wavelength of the wave in the mesosphere were calculated to be 37.8 ms-1 and 553 km. These results thus provide not only an unambiguous evidence for the vertical coupling of atmospheres engendered by the tropical cyclone Nilofar, but also the characteristics of waves that exist during such cyclonic events.


Reference:
Poster-P-12
Session:
Daily poster session during coffee breaks
Presenter/s:
Ravindra Pratap Singh
Topic:
1) Observed trends and long term variations in the middle atmosphere
Presentation type:
Poster
Room:
Pavilion
Date:
Monday, 19 September 2016
Time:
17:35 - 17:35