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Diagnosing Transient Eddy Signatures in Brightness Temperature in the Ensemble Mars Atmosphere Reanalysis System (EMARS)

Presentation #213.07 in the session Martian Aurora, Atmosphere, Winds, and Dust (Poster + Lightning Talk)

Published onOct 23, 2023
Diagnosing Transient Eddy Signatures in Brightness Temperature in the Ensemble Mars Atmosphere Reanalysis System (EMARS)

The Ensemble Mars Atmosphere Reanalysis System (EMARS) assimilates retrievals from MGS-TES and MRO-MCS into the GFDL/NASA MGCM using ensemble data assimilation (Greybush et al., 2019a). A scientific objective of EMARS is to better model and understand regional and global dust storms (GDS), particularly characterizing which atmospheric states are associated with dust storm initiation and evolution. Since regional dust storm genesis has been linked to baroclinic wave activity, EMARS requires well-characterized conditions in the atmosphere at altitudes associated with peak baroclinic wave activity. For some of the times and locations associated with these waves, the MCS retrieval success rate is reduced such that the ensemble struggles to converge on a unique synoptic state (Greybush et al., 2019b), indicating that EMARS needs additional constraints to support a comprehensive investigation of near-surface wave activity. Brightness temperatures (TBs) are measurements of radiant power directly influenced by surface temperatures, atmospheric temperatures, and aerosols that can be assimilated to improve representation of the lower Martian atmosphere. Hinson and Wilson (2021) showed signatures of TB transient eddy activity in MCS data, indicating that these data may provide the needed observational constraints for EMARS. An outstanding question is to what extent transient eddies observed in TB are the result of surface or near-surface air temperature fluctuations or dust being carried by transient eddies. To answer this, the climatology of eddy signatures in various physical indicators, such as surface temperature or pressure-normalized aerosol opacity, is constrained from the EMARS datasets. Variability from seasonal fluctuations and background dust loading is assessed by comparing GDS and non-GDS years. Preliminary results indicate eddy signatures in various TBs have similar seasonality to observational datasets, albeit with reduced TB amplitudes. Eddy activity is well-aligned with the ice cap edge, as expected due to increased baroclinicity from the meridional surface temperature gradient. However, there is longitudinal variability in propagation speed for several physical indicators in the southern hemisphere, which is under further investigation. Quantifying the relative impact of physical contributors in the eddy signatures assists in properly evaluating the use of TB in the assimilation process. This work is a step toward using TB observations in the next version of EMARS to improve representation of transient eddies.

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