Diurnal nonmigrating tidal oscillations forced by deep convective clouds

The global distribution of latent heat released by the diurnal oscillations in deep convective precipitating clouds is investigated as a forcing mechanism of diurnal nonmigrating atmospheric tidal modes. The seasonal distribution of this forcing is deduced from 3-hour temporal resolution infrared (11 mu m) radiance measured by four geostationary and two polar orbiting satellites which was transformed into the zonal wavenumber domain yielding migrating and non-migrating oscillations. The dominant wavenumbers in the forcing include the westward propagating 5, 2, and 1 oscillations, the eastward propagating 3 oscillation, and the standing oscillation. These dominant wavenumber oscillations were decomposed into Hough functions to describe their meridional structure. A vertical profile of latent heating rate was estimated and the dominant 22 tidal modes were used in an f plane model to determine the middle atmospheric response to this tropospheric forcing. The f plane model was also excited using heating rates associated with the solar insolation absorption by water vapor. The magnitude of the model atmosphere diurnal winds from both water vapor and latent heat is similar at certain locations. This response suggests that the superposition of many nonmigrating tidal modes forced by the latent heat release of precipitating clouds is important in understanding the middle atmospheric circulation.