Eddy mixing efficiency in the middle atmosphere (and elsewhere) is key to modeling accurately the transport and mixing processes in climate models. The observational constraints for eddy mixing efficiency are still sorely lacking at the moment so there are large uncertainties in its representation in models. With the ever increasing power of computational capabilities, we are beginning to be able to simulate the details of some of the instability and turbulence evolution processes in the middle atmosphere via direct numerical simulations and thus can estimate mixing directly for those cases. For instance, in one of our three dimensional simulations of propagation of a gravity wave packet through the mesopause inversion layer (MIL), we have found that mixing is much weaker than what had been generally assumed in the past. In this presentation, we will compare simulations of propagation of a gravity wave packet through several representative stratification and shear environments (including MIL, constant stratification, and constant wind shear) and will investigate in detail the mixing and instability characteristics arising in each case.

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*email: lwang@gats-inc.com
*Preference: Oral