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B. J. Conrath (Cornell University), J. C. Pearl (NASA/GSFC), M. D. Smith (Catholic University/GSFC), P. R. Christensen (Arizona State University)
In excess of one million vertical temperature profiles have been retrieved from spectra acquired with the Mars Global Surveyor Thermal Emission Spectrometer (TES) between 14 September 1997 and 1 August 1998 (Ls = 182o - 360o). The majority of these profiles were obtained by inversion of nadir-viewing measurements in the 15-micron carbon dioxide band, yielding information from the surface up to the 0.1 mbar level (or a nominal height of about 35 km). In addition, a limited number of profiles were obtained from limb-viewing measurements up to a height of approximately 65 km at high northern latitudes. These results are used to investigate the evolution of the atmospheric thermal structure during the one half seasonal cycle covered thus far by the data. Departures of the observed temperatures from radiative equilibrium are used to diagnostically study the evolution of the atmospheric circulation. The seasonal intensification and subsequent decay of the northern (winter) hemisphere meridional (Hadley) circulation is inferred from the behavior of the adiabatic compressional heating at high latitudes in the downward leg of the cell. An associated north polar vortex inferred from latitudinal temperature gradients is found to have maximum eastward thermal wind speeds at the 0.1 mbar level in excess of 180 m/s. Two regional dust storms at mid-southern latitudes profoundly affected the thermal structure at high northern latitudes, presumably due to intensification of the Hadley circulation. Aerosol signatures observed in high northern latitude limb spectra suggest that the vortex acts as an effective barrier, with dust transported from lower latitudes up to the vortex boundary but not into the interior. Scaling arguments are used to estimate dynamic time scales associated with the meridional transport.