MARS DUST STORMS - INTERANNUAL VARIABILITY AND CHAOS

The hypothesis is that the global climate system, consisting of atmosp heric dust interacting with the circulation, produces its own interann ual variability when forced at the annual frequency. The model has two time-dependent variables representing the amount of atmospheric dust in the northern and southern hemispheres, respectively. Absorption of sunlight by the dust drives a cross-equatorial Hadley cell that brings more dust into the heated hemisphere. The circulation decays when the dust storm covers the globe. Interannual variability manifests itself either as a periodic solution in which the period is a multiple of th e Martian year, or as an aperiodic (chaotic) solution that never repea ts. Both kinds of solution are found in the model, lending support to the idea that interannual variability is an intrinsic property of the global climate system. The next step is to develop a hierarchy of dust -circulation models capable of being integrated for many years.