Coherent Structures, Fluxes and Sampling Problems Over Heterogeneous Surfaces

摘要

Observations of boundary-layer flow over heterogeneous surfaces collected fromfive recent field programs are analyzed. The spatial variation of turbulent fluxes responding to surface heterogeneity are documented for a variety of situations and provides the first study of such variations with adequately sampled surface fluxes. The data analysis also provides the first detailed examination of local circulations and mesoscale fluxes driven by spatial variations of soil moisture and transpiration. The results of these studies are being used to validate models by groups at Colorado State University, Iowa State University and Rutgers. Based on the above observational analyses, the usual bulk aerodynamic formula is modified to include the effect of generation of turbulent fluxes by, unresolved, subgrid mesoscale fluxes. In addition, the transfer coefficients for the grid-averaged fluxes are shown to be generally independent of grid size, except for cases of weak large scale flow over strong surface heterogeneity. (AN).