The investigators will conduct a comprehensive modeling effort aimed at understanding gravity wave propagation, spectral energy transfers, mean-flow interactions, and wave and turbulent transports in the mesosphere and lower thermosphere (MLT). The approach involves two modeling methodologies: a highly-parallel incompressible direct simulation code and a newly-tested spectral-element code. Specific topics to be addressed include (1) the role of instabilities in limiting gravity wave amplitudes and fluxes, (2) the competition between wave-wave interactions and local instability processes in controlling wave amplitudes, (3) the role of wave superposition in controlling interaction processes, (4) the mixing and turbulent transports of heat and momentum, and (5) the effects of gravity wave dynamics on the large-scale wave fields in the MLT. The results will help quantify important gravity wave dynamics that remain largely unknown and have significant implications for modeling gravity wave effects. These results will have application to climate change, tropospheric and space weather, solar forcing of the atmosphere, and tropospheric optical turbulence.
