Mesospheric non-migrating tides generated with planetary waves: II. Influence of gravity waves

In Part I, we demonstrated with the numerical spectral model (NSM) that non-linear interactions between planetary waves (PWs) and migrating tides could generate in the upper mesosphere non-migrating tides that have amplitudes comparable to those observed. The NSM incorporates Hines' Doppler spread parameterization (DSP) for small-scale gravity waves (GWs), which affect the dynamics of the mesosphere in numerous ways. The latitudinal (seasonal) reversals in the zonal circulation and temperature variations above 70 km, largely caused by GWs, contribute to the instabilities that generate the PWs, and the circulation filters the waves. The PWs in turn are amplified by the momentum deposition of upward propagating GWs, as are the migrating tides. The GWs thus affect the migrating tides and PWs, the building blocks of non-migrating tides. In the present paper, we present the results of two computer experiments, which indicate that the GWs also contribute significantly to the process of non-linear coupling between PWs and tides. In one, we turn off the GW source to show the effect on the non-migrating tides. In the second case, we demonstrate the effect on the standing non-migrating diurnal tide by selectively suppressing, for comparison, the time dependence of the GW momentum source for zonal wave number m=0.