Geometric properties of the subgrid-scale heat flux from field observations

Arrays of three-dimensional sonic anemometers are used to measure temperature and velocity in the atmospheric surface layer. The atmospheric data are analyzed to examine the geometric properties of the subgrid-scale (SGS) heat flux in an a priori test of various heat flux models including eddy diffusivity, nonlinear, and mixed model formulations. Results are presented as joint probability functions that show the relative orientation of the measured SGS heat flux to the various parameterizations. We find that the SGS heat flux is most likely in the plane defined by the span of the mixed model.