Dusty Deep Convection in the Mars Year 34 Planet-Encircling Dust Event.

Dusty convection, convective activity powered by radiative heating of dust, is a ubiquitous phenomenon in Mars's atmosphere but is especially deep (that is, impactful on the middle atmosphere) and widespread during planet-encircling dust events (PEDE) that occur every few Mars Years (MY). Yet the relative roles of dusty deep convection and global dynamics, such as the principal meridional overturning cell (PMOC) and the radiative tides, in dust storm development and the vertical transport of dust and water are still unclear. Here, observations from the Mars Climate Sounder on board Mars Reconnaissance Orbiter (MRO-MCS) are used to study dusty deep convection and its impact on middle atmospheric water content during the MY 34 PEDE (commenced June 2018). Additional context is provided by MRO-MCS observations of the MY 28 PEDE (commenced June 2007). This investigation establishes that a few, localized centers of dusty deep convection in the tropics formed in the initial phases of both PEDE simultaneously with a substantial increase in middle atmospheric water content. The growth phase of the MY 34 PEDE was defined by episodic outbreaks of deep convection along the Acidalia and Utopia storm tracks as opposed to less episodic, more longitudinally distributed convective activity during the MY 28 PEDE. The most intense convection during both PEDE was observed in southern/eastern Tharsis, where MRO-MCS observed multiple instances of deep convective clouds transporting dust to altitudes of 70-90 km. These results suggest that Martian PEDE typically contain multiple convectively active mesoscale weather systems.