Interferometer (HRDI) zonal mean zonal wind data. We quantify and interpret differences between previous diurnal and semidiurnal predictions, hereafter G SWM-95, and GSWM-98 results. The revised GW stress parameterization accounts for the most profound changes and leads to seasonal variability predictions that are consistent with diurnal amplitudes observed in the upper mesosphere and lower thermosphere. Unresolved differences between HRDI and other wind climatologies significantly affect MLT tidal predictions.

Abstract. The capabilities of the global-scale wave model (GSWM) [Hagan et al., 1995] are extended to include migrating thermospheric solar tides. The GSWM thermospheric tidal forcing parameterization is based on neutral gas heating calculated from first principles in the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere electrodynamics general circulation model (TIE-GCM). This is the first time that a physics-based thermospheric forcing scheme has been used in a model like G SWM. Previous two-dimensional steady state linear tidal models used exospheric temperature measurements to calibrate upper atmospheric tidal forcing. New GSWM results illustrate thermospheric tidal responses that are largely consistent with tides in the TIE-GCM. Diurnal temperature amplitudes increase with increasing solar activity, but there is no analogous diurnal wind response. The thermospheric semidiurnal tide is much weaker than the diurnal tide.Semidiurnal temperature perturbations peak in the lower thermosphere where the semidiurnal forcing maximizes. The new in situ results must be combined with the GSWM upward propagating tide in the lower thermosphere, because the upward propagating components dominate the semidiurnal response throughout the region and the diurnal response below •0130 kin. In situ forcing accounts for most of the diurnal response aloft. Our preliminary evaluation of the GSWM thermospheric predictions is inconclusive. More extensive evaluations are necessary to make a firm assessment of whether the model captures the salient features of the seasonal and solar cycle variability of thermospheric tides.

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[1] An updated parameterization for the absorption and emission of infrared radiation by water vapor has been developed for the Community Atmosphere Model (CAM) from the National Center for Atmospheric Research (NCAR). The CAM is the latest version of the NCAR Community Climate Model (CCM). This updated treatment preserves the formulation of the radiative transfer equations using the absorptivity/emissivity method. However, the components of the absorptivity and emissivity related to water vapor have been replaced with new terms calculated with the General Line-by-line Atmospheric Transmittance and Radiance Model (GENLN2). The mean absolute errors in the surface and top-of-atmosphere clear-sky longwave fluxes for standard atmospheres are reduced to less than 1 W/m 2 . Mean absolute differences between the cooling rates from the original method and GENLN2 are typically 0.2 K/d. These differences are reduced by at least a factor of 3 using the updated parameterization. The updated parameterization increases the longwave cooling at 300 mbar by 0.4 to 0.7 K/d, and it decreases the cooling near 800 mbar by 0.2 to 0.6 K/d. The increased cooling is caused by line absorption and the foreign continuum in the rotation band, and the decreased cooling is caused by the self-continuum in the rotation band. These changes in the vertical profile of longwave cooling interact strongly with the parameterization of convection. The effects on the fluxes, diabatic cooling rates, and climate state are illustrated using simulations with the new climate model.

We report on a series of numerical experiments conducted with the global-scale wave model (GSWM) and designed to investigate the effects of the quasi-biennial oscillation (QBO) on the migrating diurnal tide. Our results indicate that the diurnal tidal response in the upper mesosphere and lower thermosphere (MLT) is significantly affected by the QBO in zonal mean zonal winds, but largely insensitive to the QBO in stratospheric ozone. We discuss the variable mean wind results in light of previous analytic attempts to describe the diurnal tide in the presence of mean winds and dissipation. Our calculations do not explain the interannual tidal variations observed by the High Resolution Doppler Interferometer (HRDI) on the Upper Atmosphere Research Satellite (UARS).