Traveling waves in the Martian atmosphere from MGS TES Nadir data

We have characterized the annual behavior of martian atmospheric traveling waves in the MGS TES data set from the first two martian years of mapping. There is a high degree of repeatability between the two years. They are dominated by strong low zonal wavenumber waves with high amplitudes near the polar jets, strongest in late northern fall and early northern winter. The m = 1 waves have amplitudes up to about 20 K, are vertically extended, and occasionally extend even into the tropics. Periods for m = 1 range from 2.5 to 30 sols. Much weaker waves were identified in the south, with amplitudes less than about 3.5 K. Traveling waves with m = 2 and m = 3 are also seen, but their amplitudes are typically limited to less than 4 K, and are generally more confined near the surface. In the north, they are more evident in fall and spring rather than winter solstice, which is clearly dominated by m = I waves. Some evidence of storm tracks has been identified in the data, with accentuated weather-related temperature perturbations near longitudes 200degrees to 320degrees E for both the southern and northern hemispheres near latitude 650 at the surface. Some evidence was also found for a sharpening of longitudinal gradients into what may be frontal systems. EP flux divergences show the waves extracting energy from the zonal mean winds. When the m = 1 waves were strongest, decelerations of the zonal jet of order 30 m/(s sol) were measured. Above I scale height, the waves extract energy from the jet predominately through barotropic processes, but their character is overall mixed barotropic/baroclinic. Inertial instabilities may exist at altitude on the equatorward flanks of the polar jets, and marginal stability extends through to the tropics. This may explain the coordination of the tropical behavior of the waves with that centered along the polar jet, consistent with the ideas expressed in Wilson et al. (2002, Geophys. Res. Lett. 29, #1684) and similar to those in Barnes et al. (1993, J. Geophys. Res. 98, 3125-3148). Throughout the year, there exist large regions with the meridional gradient of PV less than zero, but they are strongest near winter solstice. Poleward of the winter jet, the regions of instability reach the surface, equatorward they do not. These regions, satisfying a necessary criterion for instability, likely explain the genesis of the waves, and perhaps also their bimodal character between surface (faster waves) and altitude (slow m = 1 waves). (C) 2004 Elsevier Inc. All rights reserved.