Simulated Atmospheric Response to Large-Scale Dust Forcing and Implications for Martian Dust Storm Growth

The response of tidal, "weather," and intra-seasonal transient eddies in a global numerical model to dust imposed in different latitudinal bands and seasons has been examined in order to investigate the impact of regional scale dust storm episodes on large-scale circulation and hence on further dust storm development. The eddy kinetic energy and surface friction speed for each eddy group were derived using wavelet analysis from multi-year simulations and statistical comparisons were made among the experiments. Results show that different eddy categories respond differently to dust storm forcing, and that the responses are dependent upon both modeled storm location and season. These responses can be cast in terms of potential positive and negative feedbacks on large-scale dust storm development and have implications for the cascade of dust storms through different scales and circulation components. The model results suggest positive feedback between northern high latitude dust forcing and weather transients in the same latitudes in Quartober (L-s = 185(degrees)-245(degrees)), which weakens or disappears in Sixtober (L-s = 295(degrees)-360(degrees)). The results also suggest positive feedback between dust heating in the tropics/subtropics and tidal eddies, which may enhance the southward transport of "flushing" storms. However, southern high latitude dust forcing suppresses northern weather transients in both pseudo-season sextons, suggesting negative feedback which may terminate northern frontal/flushing dust storm sequences and hence weaken further development of a dust storm episode through this mechanism.