Numerical Exploration of the Stable Boundary Layer

Report No. ARL-TN-323
Authors: Benjamin T. MacCall; Patrick A. Haines; David G. Grove; Wen-Yih Sun
Date/Pages: July 2008; 20 pages
Abstract: The planetary boundary layer under strong, stable stratification continues to elude quantitative description despite its relatively frequent occurrence and many years of effort. Measurements indicate that stable boundary layers (SBLs) possess complex temperature and wind structures which apparently provide favorable conditions for the development of the many interacting processes that can occur within the SBL. Consequently, SBLs are subject to sporadic overturning and turbulent episodes. The National Taiwan University/Purdue University nonhydrostatic model has been outfitted with a Reynolds stress turbulence closure scheme to provide a numerical test bed for probing these environments. The model has been efficiently parallelized for the U.S. Army Research Laboratory Major Shared Research Center advanced technology clusters, enabling runs utilizing 960 processors while only losing about 10% to communication overhead. The value of the new closure scheme can be seen when simulating the phenomenon of shear instability in a stably stratified layer. The new model shows several features that are more difficult to recreate in the previous turbulence scheme, such as rapid amplification of unstable modes and Kelvin-Helmholtz billows. Given the promise of the new model, future work has begun in more realistic conditions.
Distribution: Approved for public release
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Last Update / Reviewed: July 1, 2008