P5.3 Interscale energy transfer in convective boundary layers forced by mesoscale surface heat flux heterogeneities

Thursday, 12 June 2008
Aula Magna
David P. Tyndall, Pennsylvania State University, University Park, PA; and K. J. Davis

A mechanistic understanding of how and why a convective boundary layer (CBL) responds to heterogeneous surface forcing is essential for better parameterization of the CBL in weather and climate models. CBLs forced by meso-gamma-scale surface heat flux heterogeneities may respond with organized solenoidal motions on the scale of the heterogeneity, transient convective cells smaller than the scale of the heterogeneity, or a combination of the two. Further, a realistic surface includes heterogeneity at multiple scales, and the CBL may respond to such multi-scale forcing in a nonlinear fashion. In this study a large-eddy simulation, the Bryan-Fritsch Model, is used to examine a CBL forced by one or more one-dimensional sinusoidal heat flux heterogeneities. Spectral filtering is used to determine the interscale energy transfer between modes; the energy injected into the system at the scale of the heterogeneity is tracked as it cascades to small-scale transient convective scales or remains in an organized solenoidal motion on the scale of the heterogeneity. The results will attempt to identify the physics of energy transfer between scales, the possible existence of and mechanism behind a preferred scale of response, and degree to which CBL response to multi-scale forcing in nonlinear.
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