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R. J. Wilson (Geophysical Fluid Dynamics Laboratory/NOAA)
Midlevel (~25 km) atmospheric temperatures (T15) derived from Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) spectra indicate the presence of stationary waves and thermal tides. Stationary waves are prominent at middle to high latitudes where westerly zonal flow is indicated by the meridional temperature gradient. Longitudinal variability within 40S to 40N is dominated by topographically-forced nonmigrating thermal tides that have westward and eastward propagating components. The MGS mapping data are available at two fixed local solar times so that it is not possible to distinguish between these components or isolate the sun-synchronous tide. A comparison with Mars general circulation model (MGCM) simulations suggests that the observed wave patterns in T15 are consistent with the presence of eastward propagating, diurnal period Kelvin waves with zonal wavenumbers one and two. These waves can propagate to great heights and likely account for the observed zonal variations in thermospheric density derived from MGS accelerometer data (Keating et al. this conference). The phase and latitude structure of the simulated and observed wave 2 component of T15 matches those of the 130 km density anomaly and those of the diurnal Kelvin wave inferred from the record of surface pressure observations at the two Viking lander sites. The MGCM simulations also indicate that a mix of topographically-forced eastward and westward propagating tide components are likely present in tropical temperature profiles derived from MGS Radio Science occultations (Hinson and Wilson, this conference). Thus we show that topography can play a significant role in controlling global, regional and local scale diurnal variations in wind and temperature. This research is supported by a grant from the NASA Mars Data Analysis Program.
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