Extending our previous studies of monochromatic wave-breaking events, we present results from numerical experiments in which several gravity waves are propagating together. The two wave studies were motivated by evidence in high-resolution lidar data showing the interaction of smaller-scale gravity waves (period ~ 1-2 hr, vertical wavelength ~ 5-7 km) interacting with larger-scale waves and tides. From the data we are now able to see individual wave events and their effect on the background system. We attempt here to study these events numerically, trying to understand the results in terms of the evolution of quantities often derived from remote sensing data - the spectra, particularly the vertical wavenumber and frequency spectra. Using results from four different numerical models: i) a fully compressible, non-hydrostatic model, ii) a fixed mean flow model containing only wave-wave interactions, iii) a quasilinear model containing only wave-mean-flow interactions, and iv) a linear model we show the roles of the different types of nonlinearities in the propagation characterics of the two wave system. The simulation data are used to test the predictions of several of the current theories describing the propagation of gravity waves into the mesosphere.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics