18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Thursday, 2 August 2001
Mesoscale Environments which Characterize Severe Mid-upper Tropospheric Turbulence (formerly paper 14.4)
Michael L. Kaplan, North Carolina State University, Raleigh, NC; and Y. -. L. Lin, J. J. Charney, K. T. Waight III, A. W. Huffman, J. D. Cetola, and K. M. Lux
Poster PDF (2.1 MB)
A synthesis of meso-alpha scale observational analyses, meso-beta scale numerical simulations, and meso-gamma scale simulations will be presented. The synthesis is designed to isolate the processes which result in severe accident-producing turbulence above the planetary boundary layer. It is found that the juxtapositioning of significant horizontal momentum advection, gradients of relative vorticity, and low Richardson number cause severe turbulence. The process can be synthesized as the maximum in the cross product of the gradient of Montgomery stream function and the gradient of relative vorticity on an isentropic surface. These quantities represent the region likely to produce maxima of the time rate of change of enstrophy. Hydrostatic 6 km, nonhydrostatic 2 km, and nonhydrostatic .667 km resolution simulations of several turbulence accident-producing environments will be described. The focal point will be on three-dimensional representations of dynamical processes on isentropic surfaces. The simulation results will be compared to the times and locations of turbulence accident reports from commercial aircraft.

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