Martian South Polar Summer Dust Storms in Observations, Reanalyses, and Modeling

Abstract

Dust storms near Mars' South Pole during the perihelion and summer solstice seasons (Lₛ ∼ 250–290°) are phenomenologically distinct from martian dust storms in other locations and seasons. While they have previously been observed to increase atmospheric dust loading and warm the south polar atmosphere, they have no notable impact on the middle latitudes, tropics, or northern hemisphere. Here, we use a combination of multiple remote sensing instruments, atmosphere reanalyses, and general circulation modeling to study the evolution of dust storms near the Martian South Pole during Mars Year 30 (a prototypical year for such storms). Dust lifting preferentially occurs in the eastern hemisphere (180°–320°E) and follows the retreating seasonal CO₂ polar cap to higher latitudes as the season progresses—implicating the strong cap edge thermal forcing and katabatic flows as well as surface dust availability in driving dust lifting. Dust remains confined to the high southern latitudes during this season with strong diurnal variability in both latitudinal and vertical extents. Dust is entrained in the southern circumpolar jet stream, creating filamentation and longitudinal mixing and controlling the flow of dust back onto the polar cap. The diurnally varying atmospheric circulation (Ferrel cell) limits the mixing of dust to lower latitudes and prevents a global thermal response.