The origin, evolution, and trajectory of large dust storms on Mars during Mars years 24–30 (1999–2011)

•There are differences in duration/size/season of northern and southern sequences.•Common origination areas include Acidalia, Utopia, Arcadia and Hellas.•Large dust storms follow a few general trajectories and development styles.•Many large dust storms involve overlap of two or more dust storm sequences.•Unclear connection between a Chryse dust storm and the 2007 global dust storm. Mars Daily Global Maps (MDGM) derived from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) are used to study the distribution and evolution of large dust storms over the period from Mars years 24–30 (1999–2001). Large storms are defined here as discrete dust events visible in image sequences extending over at least 5 sols (Mars days) and where the dust covers areas beyond the origination region. A total of 65 large dust storms meeting these criteria are identified during the observational period and all are observed during the Ls=135–30° seasonal window. Dust storms originating in the northern and southern hemispheres appear to form two distinct families. All but two of the storms originating in the northern hemisphere are observed in two seasonal windows at Ls=180–240° and Ls=305–350°; while all but two of those originating in the southern hemisphere are observed during Ls=135–245°. None of the large dust storms originating in the northern hemisphere are observed to develop to global scale, but some of them develop into large regional storms with peak area >1×107km2 and duration on the order of several weeks. In comparison, large dust storms originating in the southern hemisphere are typically much smaller, except notably in the two cases that expanded to global scale (the 2001 and 2007 global storms). Distinct locations of preferred storm origination emerge from the dust storm image sequences, including Acidalia, Utopia, Arcadia and Hellas. A route (trajectory) ‘graph’ for the observed sequences is provided. The routes are highly asymmetric between the two hemispheres. In the south, for non-global dust storms, the main routes are primarily oriented eastwest, whereas in the north, the routes are primarily north–south and zonally-concentrated into meridional channels. In a few impressive cases, storms originating in the northern hemisphere are observed to “flush” through Acidalia and Utopia, across the equator, and then branch in the low- and mid-southern latitudes. The origin of the 2007 global dust storm