Wave coupling in terrestrial planetary atmospheres

The roles of gravity waves and tides in coupling lower and upper atmosphere regimes, and determining mean thermal and wind stuctures, are compared and contrasted for Earth, Mars and Venus. On Earth, gravity waves close and reverse the mean mesospheric jets and force a circulation in the meridional plane that drives the high-latitude summer mesopause (similar to90 km) to temperatures similar to130K, much colder than radiative equilibrium values. Migrating and nonmigrating tides combine to dominate the meteorology of the 80-150 kin height region. On Mars, nonmigrating tides assume even greater importance due to the extreme topography in the forcing region, and they induce longitudinal variations in density between 100 and 150 km that affect aerobraking operations. Under enhanced dust loading in the Southern Hemisphere, a thermally-direct Hadley cell (augmented by momentum flux divergences due to dissipating thermal tides) provides sufficient subsidence heating to explain the anomalously warm temperatures observed over the winter pole. The dynamical effects of gravity waves in the atmosphere of Mars have yet to be studied in earnest. On Venus, thermal tides play an key role in maintaining superrotation of the atmosphere near the cloud tops (ca. 65km), and deceleration of the circulation at higher levels. Similar to Mars' dusty atmosphere, a thermally direct Hadley cell and momentum flux divergences due to dissipating tides and other waves act in concert to determine the zonal mean wind and temperature distribution of Venus' atmosphere between 65 and 100 km. The specific contributions of gravity waves, Kelvin waves and forced Rossby waves remain to be determined, however.