Transient eddies in the TES/MCS Ensemble Mars Atmosphere Reanalysis System (EMARS)

Transient eddies are important features of Mars atmosphere weather, and are linked to the genesis of dust storms. Many previous studies of transient eddies, also known as traveling waves, generally used either spacecraft observations or model simulations alone. Reanalyses, which optimally combine observations with a forecast model, provide an unprecedented opportunity to examine these traveling weather systems: their temperature, wind, pressure signatures and structure; the evolution between various wave regimes; and their seasonality and interannual variability. Using the GFDL Mars Global Climate Model (MGCM) with the Local Ensemble Transform Kalman Filter (LETKF), we have created a six year reanalysis of both Thermal Emission Spectrometer (TES) and Mars Climate Sounder (MCS) temperature retrievals, which we name the Ensemble Mars Atmosphere Reanalysis System (EMARS). We demonstrate that the transient eddies in analyses with different assumptions in the model and assimilation system, including between EMARS and the Mars Analysis Correction Data Assimilation reanalysis (MACDA), are generally robust; EMARS and MACDA eddies are more similar to each other than their respective freely running control simulations. We also reveal lower atmosphere transient eddies derived from MCS data for the first time, and compare to those derived from TES data. MCS, as a limb sounder, demonstrates some challenges in constraining the shallow eddies in EMARS compared to reanalyses using TES nadir measurements. Ensemble reanalyses are valuable in that they provide an assessment of convergence upon a unique synoptic state. We examine the six year climatology and interannual variability of transient eddies, synoptic maps, and transitions between dominant wavenumber regimes. Finally, we compare reanalysis products to other products derived from observational data, including radio science and the Viking lander surface pressure records.