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A.F.C. Bridger (Department of Meteorology, San Jos\'{e} State University), J.L. Hollingsworth (NASA Ames/SJSU Foundation)
Using the NASA Ames Mars general circulation model (MGCM), we investigate quasi-stationary planetary-wave propagation in the middle and upper atmosphere of Mars. Quasi-stationary planetary waves (i.e., internal Rossby modes) can be forced from east-west (i.e., zonal) variations in the planet's surface properties (i.e., its large-scale topography, surface albedo and thermal inertia fields). Linear theory predicts that when prevailing winds are westerly and not too strong, forced planetary waves can penetrate well into the middle atmosphere. When mean winds are easterly (e.g., during spring and summer), such waves can not propagate vertically but instead become trapped in the lower atmosphere. Results from both nonlinear mechanistic and fully coupled (i.e., where complete interactions between forced Rossby modes, thermal tidal modes, and transient barotropic/baroclinic modes are permitted) simulations are presented. It is found that substantial stationary wave activity occurs primarily within the winter westerly polar vortex, with the largest amplitude at altitude found in the largest zonal scales. However, in simulations having deep and horizontally varying atmospheric dust loading, significant stationary wave activity is also evidenced at high altitude in the subtropics and summer hemisphere, regions well within a mean easterly zonal wind regime. The fully coupled integrations indicate significant zonally asymmetric structures over several scale heights in the subtropical easterly regime are associated with diurnally-varying circulation components (e.g., thermal tides). We also find regionally enhanced stationary meridional wave activity flux from the summer to the winter hemisphere. The extent to which the latter can be modulated by and ducted through ``localized'' planetary waveguides associated with thermal tidal modes is investigated.
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The author(s) of this abstract have provided an email address for comments about the abstract: bridger@hellas.arc.nasa.gov