Boundary Layer Coherent Structures (MBL ARI)
PENNSYLVANIA STATE UNIV STATE COLLEGE DEPT OF METEOROLOGY
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It is well known that a substantial portion of the airsea fluxes of heat, moisture, and momentum is accomplished via intermittent processes Khalsa and Greenhut 1985, processes that are poorly understood at the present time. Recently, Mahrt 1989 and Sikora and Young 1993 have demonstrated that coherent structures in the marine boundary layer MBL are responsible for this flux intermittency. These coherent structure types include such secondary circulations as two-dimensional rolls cloud streets, three-dimensional convective cells thermals, and shear-driven eddies billows Brown 1980. These features occur in different atmospheric boundary layer thermal stratification and shear regimes some are forced primarily by thermodynamic, and others by dynamic, mechanisms. Our ultimate goal is to determine the mechanisms underlying the intermittency in airsea fluxes produced by these coherent structure types. As summarized below, we are using a variety of complementary statisticalmathematical approaches to objectively identify the spatial and temporal characteristics of these structures. Our primary data sources include both the high resolution output produced by the Penn State version of Moengs Large-Eddy Simulation LES code e.g. Schumann and Moeng 1991 and observations from the MBL ARI experiments performed in 1995 off the California coast.