31st Annual Meeting of the DPS, October 1999
Session 76. Mars Atmosphere: Structure
Contributed Oral Parallel Session, Friday, October 15, 1999, 4:00-5:30pm, Sala Plenaria

## [76.05] Modeling of Cyclo-, Fronto-genesis in the Mars Atmosphere

J.L. Hollingsworth (NASA Ames/SJSU Foundation), P.B. James (Dept.\ of Physics and Astronomy, University of Toledo), R.M. Haberle (NASA Ames)

We investigate Mars' middle and high latitude meteorological environment using a very high resolution global atmospheric circulation model. This research is motivated by recent Hubble Space Telescope (HST) observations of scimitar-shaped (i.e., comma''-like) cloud formations and large-scale dust activity in the polar region during early northern spring and summer, and, by recent Mars Global Surveyor (MGS) imaging using the Mars Orbiter Camera (MOC) of condensate cloud structures in the polar environment during this same seasonal range. Modeling the atmospheric circulation at high spatial resolution is necessary in order to illuminate processes important to local and regional dust activity, as well as condensate cloud formation, structure, and evolution within the edge of the seasonal polar caps. In particular, whether surface and/or upper-level fronts (i.e., narrow zones with enhanced mass density, momentum and thermal contrasts within individual transient baroclinic waves) can form in Mars' intense high-latitude baroclinic zone, and whether associated frontal circulations are sufficient to raise dust in high latitudes, is investigated. In this effort, a mechanistic multi-level global spectral model having T85 truncation (i.e., correponding to roughly 1.4\circ longitude-latitude resolution) with simplified physics (i.e., Newtonian relaxation to a radiative equilibrium'' mean temperature field) is employed. This modeling approach can capture consistently the initiation of baroclinic life cycles from which frontal structures can develop, such that a complete energy cascade from synoptic scale \cal O(5000 km) cyclogenesis to the subsynoptic scale \cal O(1000--2000 km) frontogenesis is possible. Such high-resolution modeling will aid in the assessment of Mars' polar climate, in particular, the circulation regimes that can develop. It will also aid in the interpretation of both Earth-based telescopic observations, and current and future-planned spacecraft imaging of the planet's high-latitude atmosphere.