Thermal tides and stationary waves on Mars as revealed by Mars Global Surveyor thermal emission spectrometer

Atmospheric temperature retrievals from thermal emission spectrometer (TES) observed radiances make possible the most complete separation of the constituent wave modes evident in Mars atmosphere to date. We use all of the data from the first aerobraking period as well as the science phasing orbits, which affords good sampling of the diurnal tides and stationary waves. TES retrievals of atmospheric temperature on a grid of pressure levels are the fundamental data set in this study. We then fit this data to selected Fourier modes in longitude and time for altitude, latitude, and L_s bins. From this we have identified the amplitudes and phases of the diurnal and semidiurnal tides, the first few (gravest) stationary waves, and a few modes which arise because of couplings between sun-fixed tides and topography. We also retrieve estimates of the zonal and time of day mean temperature meridional cross sections and their rates of change. The zonal and time of day mean temperature meridional cross sections agree with those of Conrath et al. [this issue] to within 1 K where we can reliably retrieve this mode (90°S to ∼20°S). Heating rates of up to 2.4 K/sol were observed around three scale heights above 60°S-90°S during the L_s = 310° - 320° dust storm. Diurnal tide amplitudes of greater than 8 K were observed during the Noachis and L_s = 310° - 320° dust storms. From L_s = 255° - 285° an unexplained phase reversal at two scale heights was observed in the diurnal tide from 60°S-80°S. Convective penetration above the unstable boundary layer may explain anomalous (180° out of phase with the sun) diurnal tide phases between 0.5 and one scale height above the subsolar point. Semidiurnal tides are of order 2 K throughout the southern extratropics. A stationary mode of wavenumber one was observed with amplitude 1-4 K in the southern extratropics. Topographically coupled tidal modes were also quantified.