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J. R. Murphy, S. Nelli (New Mexico State University)
Surface meteorology data collected by the Mars Pathfinder lander at its northern subtropical landing site during northern summer indicate the presence there of small-scale convective vortices. These atmospheric dynamical features arise in response to the strong thermal difference (superadiabatic lapse rate) between the solar-radiation warmed daytime surface and the overlying cooler atmosphere.
These vortices possess the potential to lift dust from the surface, and thus might be an important component in both maintaining a background dust haze and in engendering conditions conducive to development of larger scale dust storms. We have determined the 'climatology' of occurrence of such vortices during northern summer. This determination involves analysis of the complete pressure data set, with numerical identification of those times when a statistically significant depression (5-40 microbars in magnitude) passes over the lander site. Confirmation of occurrence is subsequently obtained by visual inspection of the data itself and commensurate signatures in the wind direction and preliminary speed data.
We will present results of this derived diurnal variation of vortex occurrence, and in conjunction with lander camera and orbiting observations of purported dust devils, speculate upon the quantity of dust these dynamical features might add to the atmosphere over seasonal cycle.