A SIMULATED SPECTRUM OF CONVECTIVELY GENERATED GRAVITY-WAVES - PROPAGATION FROM THE TROPOPAUSE TO THE MESOPAUSE AND EFFECTS ON THE MIDDLE ATMOSPHERE

This work evaluates the interaction of a simulated spectrum of convect ively generated gravity waves with realistic middle atmosphere mean wi nds. The wave spectrum is derived from the nonlinear convection model described by Alexander et al. [1995] that simulated a two-dimensional midlatitude squall line. This spectrum becomes input to a linear ray t racing model for evaluation of wave propagation as a function of heigh t through climatological background wind and buoyancy frequency profil es. The energy defined by the spectrum as a function of wavenumber and frequency is distributed spatially and temporally into wave packets f or the purpose of estimating wave amplitudes at the lower boundary of the ray tracing model. A wavelet analysis provides an estimate of thes e wave packet widths in space and time. Without this redistribution of energies into wave packets the Fourier analysis alone inaccurately as sumes the energy is evenly distributed throughout the storm model doma in. The growth with height of wave amplitudes is derived from wave act ion flux conservation coupled to a convective instability saturation c ondition. Mean flow accelerations and wave energy dissipation profiles are derived from this analysis and compared to parameterized estimate s of gravity wave forcing, providing a measure of the importance of th e storm source to global gravity wave forcing. The results suggest tha t a single large convective storm system like the simulated squall lin e could provide a significant fraction of the zonal mean gravity wave forcing at some levels, particularly in the mesosphere. The vertical d istributions of mean flow acceleration and energy dissipation do not m uch resemble the parameterized profiles in form because of the peculia rities of the spectral properties of the waves from the storm source. The ray tracing model developed herein provides a tool for examining t he role of convectively generated waves in middle atmosphere physics.