36th DPS Meeting, 8-12 November 2004
Session 37 Mars Atmosphere
Poster II, Thursday, November 11, 2004, 4:15-7:00pm, Exhibition Hall 1A

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[37.09] The Influence of Non-LTE Effects in the Martian Atmosphere on 15\mum CO2 Limb Temperature Retrievals

W.C. Maguire, J.C. Pearl, M.D. Smith (NASA/GSFC), B.J. Conrath (Cornell), A.A. Kutepov (NAS/NRC at GSFC and Max Planck), A.G. Feofilov (Munich), P.R. Christensen (Arizona State)

The 15\mum CO2 infrared band is used to derive both nadir and limb temperature profiles from MGS/TES data. For limb temperature retrievals, above about 95 km in Marsí atmosphere non-LTE effects in this CO2 vibrational bending manifold become important, but also contribute to observed radiances at lower limb tangent-point altitudes. Inputting a temperature profile characteristic of the Mars atmosphere to our non-LTE routine, we generated the corresponding 15\mum MGS/TES limb radiances accounting for non-LTE effects. We then ran this same routine in its LTE mode. In the range of 50-70 km tangent-point altitudes, the temperatures retrieved assuming LTE vary significantly (up to 10K) from the input model non-LTE temperatures. Similar differences were found with a different temperature inversion routine which assumes LTE. To parameterize these corrections, temperature profiles have been inverted for a number of martian seasons. Additionally, for these tangent-point altitudes we have found the retrieved profiles to be somewhat insensitive to the value assumed for the CO2-O collisional deexcitation rate. On the other hand, at tangent-point altitudes above the range considered here, the effect of the assumed deexcitation rate (laboratory results vary) becomes progressively more significant, as is already well-known.

Funding for this research was provided by NASA through its Mars Data Analysis Program. We also acknowledge support by NASA for an NAS/NRC Associateship.

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