Comparative Evaluation of Eddy Exchange Coefficients for Strong and Weak Wind Stable Boundary Layer Modeling

Abstract

Five local K-closure formulations and a TKE closure were incorporated in a one-dimensional version of the Pielke?s model, and a comparative evaluation of the closure schemes was made for strong and weak wind stable boundary layer (SBL). The Cabauw (Netherlands) and EPRI-Kincaid site (United States) observations were used for this purpose. The results indicate that for the strong wind case study, the profiles of turbulent diffusivities in terms of shape, depth of significant mixing, and the height above the surface where diffusion reaches a maximum are more or less the same for the various closure schemes. Only the magnitudes of mixing produced by various closure schemes are different. This difference produced by various closure formulations causes minor but noticeable changes in the mean wind field and thermodynamic structure of the model SBL. However, although the profiles of turbulent diffusivities become weak, variable, and poorly defined under weak wind conditions, the mean profiles become insensitive to the differences in the diffusion that arise due to various parameterization schemes. Apart from the TKE closure scheme, Estournel and Guedalia simple local closure scheme is able to produce the essential features of the SBL quite well.