Deep Convective Activity in the Mars Planet-Encircling Dust Event 2018a: Observations by the Mars Climate Sounder
Abstract
Deep convection is widely used in the astronomical and geophysical sciences to refer to characteristically intermittent, mesoscale circulations that efficiently transport constituents and/or heat and momentum across large-scale mixing barriers and to a variety of processes that drive these circulations. On Mars, convection associated with the buoyancy generated by the solar heating of dust ("dusty convection") is energetically analogous to moist convection in the Earth's atmosphere. In regional and global dust storm activity, dusty convection can bring air from the lower atmosphere to 60-80 km altitudes on sub-diurnal timescales, implying that updraft velocities in dusty deep convection on Mars may be similar to those in moist deep convection on Earth. We have argued and demonstrated in part that this transport may drive seasonal and interannual variability in hydrogen escape from Mars by increasing water vapor concentrations in the middle atmosphere, where water vapor can be dissociated efficiently by ultraviolet radiation.
During the 2018a Mars planet-encircling dust event, there were multiple instances of exemplary dusty deep convection observed by Mars Climate Sounder on board Mars Reconnaissance Orbiter. The dataset also allows regions where dusty deep convection was rare to be identified. We will place the observed structures in the context of theory and observations of past regional and global dust storm activity. We will emphasize three important points. First, deep convection in such a storm mostly occurs during discrete episodes concentrated in a few areas of Mars. Second, the horizontal extent of mixing above 60 km depends on how the large-scale wind field distributes outflow from deep convective centers, a function of both season and deep convective center location. Third, the most intense vertical mixing on Mars under any circumstances seems to be associated with intense lifting over Syria Planum merging with an orographic circulation over Pavonis Mons.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P43J3859H
- Keywords:
-
- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5445 Meteorology;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS