ITR/AP: Small-Scale Dynamical Interactions with Chemical Processes in the Terrestrial Upper Atmosphere

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A three-year funding period is being requested so that the PI can expand and modify his existing simulation code in order to relax key assumptions that were previously implemented only because of computational constraints. His numerical simulations describing the interaction of small-scale gravity waves with minor species and related chemical processes in the mesopause region (90 km altitude) are the most complete and realistic to date. Quite apart from causing large, highly nonlinear oscillations in minor species number densities, the waves drive a large downward transport of minor species through the effects of dissipation. In spite of the fact that the model simulates time-dependent interactions between dynamics and nonlinear chemistry, the model uses linear (versus nonlinear) dynamics and a very limited number (or incomplete set) of chemically active minor species. These simplifications have been necessary in order to be able to run the code within a reasonable amount of time on stand-alone personal computers. However, to gain a complete understanding of the interactions and in order to include both physical and chemical processes that are known to be important in this region of the atmosphere, these two idealizations will have to be relaxed. This will increase the computational burden well beyond the limits of personal computers, requiring multiprocessor computers for faster, efficient computations. The PI is thus proposing to purchase a relatively inexpensive "turn-key" multiprocessor machine to assist them in the in-house development and testing of code required to increase the level of realism in their model, and subsequently transfer the code to faster super-computers at the National Center for Atmospheric Research. The proposed work falls into the Applications in Science and Engineering (AP) section of the small class category of ITR proposals, and is most closely related to the Aeronomy Program of the Atmospheric Science Division within the Directorate for Geosciences.