Enhanced Super‐Rotation Before and During the 2018 Martian Global Dust Storm

Super‐rotation affects—and is affected by—the distribution of dust in the martian atmosphere. We modeled this interaction during the 2018 global dust storm (GDS) of Mars Year 34 using data assimilation. Super‐rotation increased by a factor of two at the peak of the GDS, as compared to the same period in the previous year which did not feature a GDS. A strong westerly jet formed in the tropical lower atmosphere, with strong easterlies above 60 km, as a result of momentum transport by thermal tides. Enhanced super‐rotation is shown to have commenced 40 sols before the onset of the GDS, due to dust lifting in the southern mid‐latitudes and tropics. The uniform distribution of dust in the tropics resulted in a symmetric Hadley cell with a tropical upwelling branch that could efficiently transport dust vertically; this may have significantly contributed to the rapid expansion of the storm. Plain Language Summary Dust plays a major role in driving the behavior of the atmosphere of Mars. During a global dust storm (GDS), winds lift, and transport dust throughout the atmosphere; in turn, dust affects wind direction and strength by heating and cooling the surrounding air. Using a technique that combines satellite observations with simulations of the martian atmosphere, we demonstrate that winds at tropical latitudes were greatly strengthened during the 2018 GDS as a result of heating by dust. We show that tropical winds were strengthened even before the onset of the storm, as a result of a dust‐driven modification to the tropical circulation pattern. This change in the tropical circulation may have played a role in the formation of the GDS. Key Points The martian atmosphere was already in a state of enhanced super‐rotation prior to the onset of the Mars Year 34 global dust storm Super‐rotation doubled during the peak of the storm and tropical easterlies were strongly enhanced above 60 km Dust lifting in the southern hemisphere led to enhanced tropical heating and increased vertical dust transport in the lead‐up to the storm