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D. Banfield (Cornell), J.R. Barnes (Oregon State), B.C. Conrath (Cornell), J.C. Pearl, M.D. Smith (NASA Goddard), P. Christensen (Arizona State)
Our goal is to detect and quantify the presence, locations, amplitudes, speeds, wavenumbers, vertical structures and lifetimes of travelling waves in Mars atmosphere as a function of season. The data we employ are atmospheric temperatures from Mars Global Surveyor's (MGS) Thermal Emission Spectrometer (TES). Viking lander observations showed highly coherent (~20 sol), low wavenumber (m~2-5), moderate amplitude (~4K) travelling waves. Modelling efforts have suggested that baroclinic activity in the southern hemisphere is reduced compared to the northern hemisphere (where all ground-based observations of travelling waves have occurred). Previous efforts to quantify travelling waves with Mariner 9 IRIS and Viking Orbiter IRTM have not been definitive.
We have analyzed the data from MGS TES before the spacecraft entered its mapping orbit, subtracting the atmospheric variations that were systematic with latitude, longitude, time of day and season. The residuals that this left (of order 2K in standard deviation) included travelling wave temperature perturbations. However, no coherent waves propagating in longitude and time were conclusively detected for any of the data analyzed. This included only the southern hemisphere for Ls=190-278 and Ls=358-29. Outside of these ranges the coverage was either non-existent or poor. This result is in rough accord with the modelling predictions, although no observations existed in this subset for southern winter, when travelling waves there might be at their strongest.
We intend to extend this analysis to include the mapping data from MGS TES, with its excellent temporal, spatial and seasonal coverage. The approach of Salby's Fast Fourier Synoptic Mapping will likely be employed for that phase of the analysis because of the data's very regular observation pattern, although confounding effects of time changing diurnal tides may exist.
This work is supported by the NASA Mars Data Analysis Program.