Dust storms originating in the northern hemisphere during the third mapping year of Mars Global Surveyor

Data from the third Mars Global Surveyor (MGS) mapping year (MY 26, 2003-2005) are used to investigate dust storms originating in the northern hemisphere. Flushing dust storms, which originate as frontal dust storms at the northern polar vortex edge and propagate southward through topographic channels, are observed immediately before and after a quiescent period that occurs around the northern winter solstice (240°<Ls<300°). Both the pre- and post-solstice active periods can be further divided into two sub-periods. The most vigorous of these flushing storms occurred during L_s 210-220° and L_s 310-320°. The lifted dust crossed the equator and accumulated in the southern hemisphere. These major dust storms enhanced the Hadley circulation and suppressed the lower-level baroclinic eddies in the northern mid and high latitudes. The 2-3 sol wave number m=3 traveling waves show the best correlation with flushing dust storms and can combine with other wave modes to produce storm tracks and fronts within individual sub-periods.