Comparison of FFSM Transient Eddies and MOC Storms, MY 24-26

Fast Fourier Synoptic Mapping (FFSM) is a spectral analysis method that creates synoptic maps from asynoptic data, maintaining full space-time resolution without distorting or smoothing higher frequency (~1-3 sols) weather signals (Barnes 2001, 2003, 2006). This process removes the time mean, zonal mean, and westward diurnal tide. FFSM analysis of TES 3.7 hPa temperature data shows a quasi-periodic (~2-3 sol) sequence of eastward-propagating cold and warm centers that indicate the presence of baroclinic eddies in the thermal field. We have combined FFSM-filtered TES temperature anomalies with Mars Orbiter Camera (MOC) visible storms to better understand interannual similarities and differences. There appears to be a correlation between the eastward propagation of cold anomalies and eastward storm evolution. Overall eddy characteristics are similar in MY 24 and 25. An outstanding difference between the two years is the degree to which strong-amplitude eddies persist through Noachis and extend (undiminished) into Hellas. This occurs throughout the MY 25 precursor phase from Ls=174-180°. Major cap-edge storms south of Hellas occur less frequently in MY 24 MOC images compared to MY 25. Northward storm progression in MY 25 is significantly greater than other Mars years.