Stability of Atmospheric Shear Flows and Eddy Characteristics

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Professor Mahrt will reexamine the development of shear- instability and generation of turbulence in stratified flow by employing nonlinear stability analysis techniques (energy-Casimir approach). Preliminary work indicates that the critical Richardson number is generally larger than 0.25 but depends on the curvature of mean flow profile. While this stability analysis is more general than previous analyses, a number of technical points must be examined before results can be developed with confidence. Most interesting are differences predicted by this approach and those of Ekman instability. These analytical results will be compared to an unprecedented large sample of high-quality tower data collected in stable conditions over flat terrain (Riso, Denmark) and will also be applied to fast response aircraft data collected above the boundary later in several meteorological field experiments. The objective is to assess the relationship between turbulence development and the mean profile of wind and potential temperature.//