CAWSES Projekt - NMT-MLT

Seasonal and interannual variability of nonmigrating tides in the mesosphere and lower thermosphere.

Dr. Jens Oberheide
Bergische Universität Wuppertal
Fachbereich C - Mathematik und
Naturwissenschaften (Physik)
Gaußstraße 20
42097 Wuppertal
joberh@uni-wuppertal.de

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The scientific objective of this proposal is the analysis of the structure and the seasonal and interannual variability of nonmigrating tides in the mesosphere and lower thermosphere (MLT). Zonal and meridional wind measurements of the TIMED Doppler Interferometer (TIDI) will be Fourier analyzed on diurnal and semidiurnal nonmigrating tides from 85-105 km altitude and from pole to pole. This effort will provide the observational database for the science investigations. Observation-based tidal definitions are also expected to aid modelers in tuning source functions and dissipative parameters to match observations.

The observed tides will be correlated with Quasi Stationary Planetary Waves (QSPW) from assimilated NCEP/CPC data. One goal is to consolidate model predictions that interactions of solar driven migrating tides with QSPWs play an important role in nonmigrating tidal forcing. This process and additional latent heat release in the troposphere imply that large-scale tropospheric systems that do not propagate into the MLT can nevertheless modulate the solar tides in that region. Comparative analyses of the observations with the results of a linear (GSWM) and of a general circulation model (TIME-GCM) will be conducted to identify the sources of the nonmigrating tides and their variability, including solar cycle and storm effects.

NMT-MLT