Strategies for Analysis of Martian Dust

Characterizing the distribution and temporal evolution of dust in the Martian atmosphere is a considerable challenge. Spacecraft observations are sparse and have limitations in vertical coverage, dust physical properties are not well known, and model parameterizations of surface lifting have limited success in reproducing observed variability. We review several methods for generating a dust reanalysis, including column opacity analysis, non-Conrath vertical distributions via adjustments to model tracer fields, ensemble data assimilation of dust profiles, opacities inferred through surface brightness temperatures, surface dust flux estimation, and dust parameter estimation. We then describe dust distributions in the most recent version of the MGCM-LETKF Mars reanalysis. Current results are from two DAS, one assuming a fixed dust distribution and one using TES opacities and updating the boundary layer dust. In these reanalyses, a full year of Thermal Emission Spectrometer (TES) temperature profiles have been assimilated.

Since an accurate characterization of the sources and sinks of dust would greatly improve our understanding of the Martian dust cycle and its representation in numerical weather prediction models, we will examine an advanced DAS technique that have been demonstrated in terrestrial DAS and could be applied to the problem -- surface dust flux estimation. The surface flux method requires no a priori information about the fluxes, and uses only atmospheric observations. For the terrestrial CO2 problem, surface sources and sinks of CO2 have been estimated using only time-dependent measurements of atmospheric CO2, temperatures, and winds, and without a priori information on the surface fluxes. This scenario is very analogous to the case of Mars. On Mars we have only information on temperature and dust opacities at spacecraft overpass locations. Results for terrestrial CO2 and plans for Mars dust will be presented.