Simulations of Diurnal tides due to tropospheric heating from the NCEP/NCAR reanalysis project

Abstract

Diurnal tides are forced in a global-scale wave model using monthly mean tropospheric heating rates from the NCEP/NCAR Reanalysis Project. The heating rates give rise to a semiannual variation in the migrating (sun- synchronous) tidal wind response near 95 km altitude with equinoctial maxima (~50-70 ms-1) similar in magnitude to those derived from observational data. Nonmigrating (longitude-dependent) tides with zonal wavenumbers s = -3 (eastward) to s = +5 (westward) are also generated. Many of these oscillations are characterized by wind and temperature amplitudes of order 20-30 ms-1 and 10-20 K in the lower thermosphere (100-130 km), and suggest that the tidal response in this regime varies considerably with longitude.