Examining the Martian Water Cycle Using the Mars Climate Sounder (MCS) and Ensemble Mars Atmosphere Reanalysis System (EMARS)

In this study we use the Ensemble Mars Atmosphere Reanalysis System (EMARS), which assimilates Mars Climate Sounder (MCS) retrievals, to examine the water cycle in the Martian polar regions. The advantage of using a reanalysis is that full model fields of temperature, wind, and water ice and vapor are available at hourly frequency, even in the absence of direct measurements of water vapor. The reanalysis is dynamically guided by available temperature profile retrievals from the Mars Climate sounder and and by gridded dust column opacity through the data assimilation process. Zonal mean and time averaged fields, as well as time evolving fields and eddies, are examined between observations, a freely running model without data assimilation, and EMARS to discern the climatology and weather that govern the water cycle. There appears to be greater cross-vortex transport in EMARS than its control run, in particular at middle-tropospheric pressure levels between 10 and 100 Pa. EMARS simulations show a stronger variability in the region of the polar vortex edge due to weather, and better represent traveling waves than the free-running model. This suggests that eddies play an important role in the process of cross-vortex boundary transport.