The goal of this project is to better understand wave coupling mechanisms and their role in the dynamics of the Earth's middle atmosphere. The investigators will examine the tidal/planetary wave, tidal/gravity wave and planetary/gravity wave couplings in the Mesosphere and Lower Thermosphere (MLT) region of the atmosphere by employing data from a complementary general circulation model, the extended Canadian Middle Atmospheric Model (CMAM). They will use modeled data (including temperature, winds, gravity wave forcing) over an annual cycle from the extended CMAM, a full, three-dimensional, self-consistent, and spectral general circulation model from the Earth's surface to about 210 km, to study the physical mechanisms of the interaction processes in tidal/planetary wave and tidal/gravity wave and their role in the momentum budget of the atmospheric tides. They will also employ the one-year modeled data from the extended CMAM (such as winds, geopotential height, and gravity wave forcing) to study the possible consequence of the planetary/gravity wave coupling - generation of large-scale planetary waves in the upper mesosphere and lower thermosphere region of the Earth's atmosphere. Further understanding of the upward propagation and latitudinal-propagation of the planetary waves in the upper mesosphere and lower thermosphere will be also achieved. The study will lead to a better understanding of the processes that govern the coupling, energetics and dynamics of the middle and upper atmosphere. The project also addresses the complexity of nonlinearity, a crucial element that needs to be understood within the space atmosphere interaction region (SAIR) in order to better predict 'space weather'. Furthermore, the work is highly relevant to the efforts of the international Climate and Weather of the Sun-Earth System (CAWSES) research community. The project supports efforts to expand atmospheric dynamics research in Kentucky through support of a graduate research assistant.