Midlatitude weather systems on Mars: Is there a hemispheric asymmetry?

The Viking Lander meteorology observations confirmed that midlatitude weather systems are present in the Northern Hemisphere of Mars during the autumn, winter, and early spring. These systems have properties consistent with a development through baroclinic instability of the wintertime zonal-mean circulation. It is known that the weather systems must be of importance for the zonal-mean circulation by virtue of their heat and momentum transports. Observations show that they are associated with dust raising, and they must be involved in the transport of dust; the weather systems almost certainly must act to produce significant water transports as well. Recent simulations with the ARC Mars General Circulation Model (GCM) show that the heat transports by the weather system (and by the zonal-mean circulation) during northern winter can be very substantial: large enough to significantly reduce the CO2 condensation at polar latitudes. This could be largely responsible for the observed early spring halt in the north polar cap recession and for the presence of westerly winds near the cap edge during this season.