DPS 2001 meeting, November 2001
Session 27. Mars Atmosphere I: Circulation
Oral, Chairs: J. Hollingsworth, A. Toigo, Thursday, November 29, 2001, 10:30am-12:30pm, Regency E

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[27.06] Asynoptic Fourier Transform Analyses of MGS TES Data: Transient Baroclinic Eddies

J.R. Barnes (Oceanic and Atmospheric Sciences, Oregon State U.)

Transient baroclinic eddies have been known to be present in the Martian atmosphere since the Viking Mission. Analyses of Viking Meteorology data revealed large-amplitude weather systems were present in middle latitudes except during summer. GCM studies have shown that the transient baroclinic eddies are important components of the general circulation, acting to transport heat polewards and upwards. In the GCM simulations the eddies are very deep, exhibiting maximum wind amplitudes at high levels (30-50 km). The eddies are of planetary scale, being characterized by zonal wavenumbers of 1-4. Perhaps the most interesting aspect of the GCM baroclinic eddies is that they are much weaker in southern than in northern winter. This is a consequence of the large eccentricity of the Mars orbit, and it also appears to be a result of the very hemispherically asymmetric topography of Mars.

The MGS TES instrument has acquired more than one Mars year of mapping orbit atmospheric temperature data, allowing the detection of the slowly propagating baroclinic eddies. The Asynoptic Fourier Transform method of analysis is well suited to the TES mapping data set, since it allows the maximum wavenumber-frequency resolution of the data to be realized without smoothing higher-frequency modes. We have applied Asynoptic Fourier Transform analysis to the TES data, to begin determining the basic properties of the transient baroclinic eddies in both hemispheres and all seasons. The initial focus has been upon the solsticial seasons, for which the GCM studies show the greatest differences between northern and southern hemispheres. The analyses allow the zonal wavenumbers, periods, and latitude-height structures of the baroclinic eddies to be determined. We will report results from the early stages of our studies of the TES data, focusing on the basic hemispheric asymmetry of the eddy activity, in addition to definition of the basic eddy properties and comparison of these to GCM results.

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