Climatic Impacts and Transport of Martian Atmospheric Dust from Assimilation of Spacecraft Observations

Streeter, Paul (2020). Climatic Impacts and Transport of Martian Atmospheric Dust from Assimilation of Spacecraft Observations. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.00011eb1

Abstract

Mars' dust cycle and the radiative-dynamical impacts of atmospheric dust were investigated by assimilating Mars Climate Sounder (MCS) temperature and dust observations into a martian global climate model. Dust plays a key role in Mars' climate by interacting with solar and infrared radiation, thereby modifying atmospheric dynamics and winds, which themselves lift and transport dust. The 2018 Global Dust Storm (GDS) provided an opportunity to investigate how dust affects martian surface temperatures, polar dynamics, and the dust cycle.

The 2018 GDS was found to warm the martian surface by 0.9 K. The effects were highly spatially heterogeneous, with net warming from enhanced backscattering of surface infrared emission at low thermal inertia regions, while elsewhere blocked incident solar radiation caused net cooling. Comparisons with the 2001 GDS and free-running simulations show that GDS geographical structure is key in determining the surface temperature impact.

Martian dust lifting and deposition were shown to have a consistent interannual pattern, except during planetary-scale dust storms. Dust lifting patterns correspond to regular dynamical features including baroclinic waves, low-level jets, and CO2 sublimation flow. Regional dust storms affect southern seasonal cap-edge dust lifting by enhancing the meridional circulation, causing increased sublimation. The 2018 GDS increased dust lifting over high-topography regions like Tharsis, but inhibited northern wave-related dust lifting. Southern high-latitude winds were found to be highly sensitive to the precise thermal structure in MCS temperature observations, with direct impacts on dust lifting.

The 2018 GDS was found to alter the elliptical structure of Mars' polar vortices via the GDS' effect on stationary topographic planetary waves, proving the link between these waves and vortex morphology. Enhanced GDS heating also significantly accelerated the destruction of the southern vortex. These results show the asymmetrical effects of an equinoctial GDS on the polar vortices, which govern tracer transport into polar regions.

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