DPS 34th Meeting, October 2002
Session 15. Mars
Poster, Chair(s): , Tuesday, October 8, 2002, 3:30-6:00pm, Exhibit Hall

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[15.11] Water Ice Clouds: Comparing the MGS and Viking Eras

A.S. Hale, L.K. Tamppari (JPL), P. Christensen, J. Pearl (arizona state university), D. Bass (JPL)

Water ice clouds were once thought not to be a significant player in the Martian water cycle and climate. However, work by Clancy et al. (1996) has indicated that water-ice clouds may indeed play a major role by trapping water in the northern hemisphere during northern summer via the aphelion cloud belt. At the time of their work, the aphelion cloud belt was not recognized as an annual feature in the Martian climate and was proposed to be due to a climate change since Viking. Tamppari et al. (2000), showed that the aphelion cloud belt was present during the Viking era, and in fact, the Martian atmosphere exhibited widespread and frequent water-ice clouds throughout the Martian year. Subsequently, water-ice clouds, and specifically the aphelion cloud belt, have been seen through the MGS TES data set (Smith et al., 2001a, 2001b; Pearl et al., 2001).

Tamppari et al. (2000) used Viking IRTM data to map water-ice clouds in the Martian atmosphere; we are continuing this work with MGS TES data in order to compare the Viking and MGS eras with as similar techniques as possible. Such a comparison is important not only to expand the existing data set, but to better understand the interannual differences in water-ice cloud coverage. In order to compare the two datasets we generate synthetic-IRTM data from TES and construct maps in the same manner as Tamppari et al. (2000). The cloud detection scheme separates the surface and atmospheric contributions via a surface thermal model with thermal inertias, albedos, and wavelength-dependent emissivities applied. Previous maps (Tamppari et al., 2001) used values derived from the Viking data set for these inputs. In the current work, we compare TES emissivities to IRTM derived values to determine if the surface models need updating. Preliminary maps and results will be presented.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.