Modeling diurnal tidal variability with the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model

We used the National Center for Atmospheric Research thermosphere-ionospher e-mesosphere-electrodynamics general circulation model (TIME-GCM) to calcul ate the variability of the migrating diurnal tide in a January through Dece mber 1993 simulation. While TIME-GCM captures the salient features of the l atitudinal, altitudinal, and seasonal variability of the migrating diurnal tide, upper mesospheric meridional wind amplitudes are somewhat smaller tha n those that have been observed from the ground and space. The discrepancie s may be attributable to unresolved uncertainties in tidal forcing and/or d issipation in the TIME-GCM. However, our diagnostic simulation suggests tha t the nonlinear interactions between the migrating diurnal tide and station ary planetary wave 1 produce measurable nonmigrating diurnal tidal componen ts that modulate migrating diurnal tidal amplitudes and account for signifi cant variability in the upper mesosphere and lower thermosphere.