DPS 2001 meeting, November 2001
Session 27. Mars Atmosphere I: Circulation
Oral, Chairs: J. Hollingsworth, A. Toigo, Thursday, November 29, 2001, 10:30am-12:30pm, Regency E

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[27.04] GCM simulations of the current Martian water cycle: clouds and dynamical leverage

A.V Rodin (Space Research Institude, Moscow), R.J. Wilson (GFDL/NOAA), M.I. Richardson (Caltech)

A multiannual simulation of the current Martian climate has been carried out with the GFDL Mars general circulation model (MGCM) that includes atmospheric transport of dust and water, as well as microphysics and the radiative effects of water ice clouds. Simulations show good agreement with the recent water column retrievals from TES data. The apparent differences with Viking observations suggest that the MAWD data were biased by the shielding of water vapor absorption features by dust. The North tropical maximum of water column observed by TES in the perihelion season (South winter) is reproduced in the GCM simulations and coincides with the downward branch of the Hadley cell. Its counterpart in the aphelion season is missing because of the condensational cutoff of atmospheric water in the tropical upward branch of the Hadley cell that produces the aphelion season tropical cloud belt. A series of parametric sensitivity tests carried out with the model shows that both the seasonal trends and latitudinal gradients of water column are largely controlled by the intensity of Hadley circulation. In particular, in the aphelion season, a more intense circulation results in stronger latitudinal gradients and shorter period of rapid water vapor release from the North polar cap. By contrast, a weaker circulation results in smoother latitudinal extent of atmospheric water. In the equinoctial seasons when the circulation intensity is weakest, it remains responsible for the appearance of the precursor maxima of water vapor in the extratropics in the spring hemispheres. As the intensity of the Hadley circulation is sensitive to the thermal state of the atmosphere, the water cycle is, in part, controlled by the microphysical and radiative properties of water ice clouds, with sensitivity of this control channel being rather smooth. There is no evidence, however, that the adsorbing capability of the regolith has an equally important leverage on the Martian water cycle.

The author(s) of this abstract have provided an email address for comments about the abstract: rodin@irn.iki.rssi.ru

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