36th DPS Meeting, 8-12 November 2004
Session 26 Mars Atmosphere I: Methane and High Altitude
Oral, Thursday, November 11, 2004, 8:30-10:00am, Lewis

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[26.07] Comparison of Atmospheric Temperatures Obtained Through Infrared Sounding and Radio Occultation by Mars Global Surveyor

D. P. Hinson (Stanford University), M. D. Smith (GSFC), B. J. Conrath (Cornell University)

Mars Global Surveyor (MGS) monitors temperatures in the Martian atmosphere through infrared sounding by the Thermal Emission Spectrometer (TES) as well as Radio Science (RS) occultation experiments. We report results from extensive comparisons of TES nadir and RS temperature profiles, focusing on data obtained under conditions that allow nearly simultaneous measurements at the same location and local time. We analyzed data from 13 intervals with durations of 7--19 sols that sample latitudes of 62o--85oN during midspring through early autumn. Our results generally confirm the accuracy and reliability of both sets of observations. We find particularly good agreement between the zonal variations of temperature observed by the two instruments. Zonally averaged temperature profiles agree to within ~2 K at pressures <400 Pa. Results are less satisfactory at 610 Pa, where the TES retrievals are persistently warmer by a margin of 2--8 K. The RS profiles from selected intervals might contain a low-altitude bias due to the unmodeled effect of water vapor. However, these discrepancies arise predominantly from a wide disparity in vertical resolution. The RS measurements reveal subtle but significant vertical variations of temperature, particularly at low altitudes, that TES is unable to resolve. For the range of latitudes and seasons considered here, the most serious consequence is that temperature lapse rates deduced from TES profiles are unreliable in the lowest scale height above the surface. These results should contribute to a more confident characterization of Martian climate.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.