Non-migrating diurnal tides generated with planetary waves in the Mesosphere

Abstract

We report results from our Numerical Spectral Model (NSM) that incorporates Hines' parameterization for small-scale gravity waves (GW). The NSM generates nonmigrating tides in the mesosphere having amplitudes comparable to those observed, and we demonstrate that they arise from interactions between migrating tides and planetary waves (PW). We examine this mechanism for the large m = 0 diurnal tide, which was proposed to be generated with m = 1 PWs. The NSM is run for comparison without the zonal mean heat source, which suppresses the PWs that normally are excited by instabilities. The resulting amplitudes of the stationary tide are then negligibly small. When the time dependent GW momentum source for m = 0 is turned off, the stationary tide is significantly reduced. This indicates that, in the NSM, GWs play an important role in generating the nonlinear interactions between migrating tides and PWs that are necessary to produce the nonmigrating tides.