The circulation of the middle atmosphere is driven by complex interactions of chemical, physical, and dynamical processes. Ideally this circulation should be simulated with a fully three dimensional model, but to do so can be computationally prohibitive. For this reason, and also in order to isolate certain processes for in-depth studies, researchers rely on simpler models for much of their work. In designing simpler models, researchers endeavor to make them as realistic as possible. Under her last award, the principal investigator coupled a quasi-geostrophic time-dependent wave model to a zonally averaged (two-dimensional) chemical- radiative-dynamical model of the middle atmosphere (principally the stratosphere). The wave model is used to determine the driving of the mean flow by Rossby waves and subsequently the eddy transport of chemical species. Her goal was to obtain more realistic simulations of stratospheric circulation and associated trace species transport than would be possible with the two dimensional model alone. With this renewal award, Dr. Smith will continue her research on the middle atmosphere. The coupled model will be made more realistic with the addition of an interactive lower boundary at the tropopause. The principal objective then will be to assess the quality of the coupled model's dynamical interactions and the ability to simulate transport of chemical species (the distribution of which also affects the circulation). The coupled model will be compared in detail with a fully nonlinear three dimensional model of the stratosphere to determine the ability of the wave model to represent transport processes.
