Comparison of the Martian Polar Vortices in Data Assimilation Reanalyses and General Circulation Models

We present a comparison and analysis of the Mars polar vortices in two atmospheric reanalyses based on the assimilation of Thermal Emission Spectrometer temperatures (the Ensemble Mars Atmosphere Reanalysis System, EMARS, using the GFDL Mars GCM and the Mars Analysis Correction Data Assimilation, MACDA, based on the LMD-UK Mars GCM) and two free running general circulation models: MarsWRF and the Ashima/MIT GCM. The martian polar vortices differ from Earth's stratospheric vortices by exhibiting an annular structure in potential vorticity, i.e., the potential vorticity in the martian polar vortices maximizes in an annulus around the pole with the pole being a local minimum. This annular structure is stable on long timescales in all four model systems. We compare the structure and evolution of the vortices between the different modeling systems, and investigate the mechanisms driving the annular structure of the vortices.