A mesoscale model for the Martian atmosphere

Abstract

The Pennsylvania State University/National Center for Atmosphere Research Mesoscale Model Version 5 (MM5) has been converted for use on Mars. Modifications are based on schemes implemented in the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model (GCM). Validation of the Mars MM5 is conducted by comparison to the Mars GCM, examining the large-scale dynamics in the two models. Agreement between the two models on similar scales (a few hundred kilometers) is good. Validation is also performed against both Viking Landers and Mars Pathfinder meteorological observations with the model run at higher vertical (lowest level at 1.6 m) and horizontal resolution (a few kilometers). We find reasonable agreement with near-surface air temperature, pressure, and wind direction observations, with caveats. The results demonstrate that the model accurately simulates surface heat balance and the propagation of global thermal tides. However, wind speeds are underpredicted. The model generates the correct phasing of wind speeds with local time at the Viking Lander 2 site during winter but does not generate the correct phasing at the other sites or seasons. We examined the importance of slopes and global tides in generating the diurnal cycle of winds at the lander sites. We find that tides are at least as important as slopes, in contrast to previous studies. This study suggests that when used in combination with a GCM, the Mars MM5 promises to be a powerful tool for the investigation of processes central to the Martian climate on scales from hundreds of kilometers to tens of meters.