Interannual variability of Martian weather

Pressure, temperature, imaging, and wind data from the Mutch Memorial Station, the Viking lander located in Mars' subtropics, are used to demonstrate the existence of two disctinct regimes of northern hemisphere winter weather on Mars. One of these regime is characterized by one or more intense global dust storms in which the optical depth reaches about 5 over most of the planet. During these events, traveling baroclinic waves of the winter hemisphere are suppressed. In the other regime, there are no global dust storms, but traveling baroclinic waves are active, and high winds associated with these storms raise large quantities of dust which remain confined to a shallow layer in the northern hemisphere. The strongest winds at the Mutch Memorial Station occur during intense storms in the latter regime.