A Surface Flux Parameterization Based on the Vertically Averaged Turbulence Kinetic Energy

Abstract

A new bulk transfer formulation for the surface turbulent fluxes of momentum, heat, and moisture has been developed by using the square root of the vertically averaged turbulent kinetic energy (TKE) in the atmospheric boundary layer as a velocity scale, in place of the mean wind speed. The new parameterization utilizes the surface radiative (skin) temperature instead of the temperature at a “roughness height.” Field observations and large-eddy simulation (LES) results were used to develop the parameterization. It has been tested using an independent dataset from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). The predicted surface momentum flux compares very well with the observations, despite the fact that the data used for developing the new parameterization have a very different roughness length from the independent FIFE data. This shows that the parameterization can represent a wide range of surface roughness boundary conditions. The predicted sensible and latent heat fluxes also agree well with the FIFE observations, although the predicted surface sensible heat flux is somewhat less than observed at the FIFE site. The diurnal cycles of the predicted surface sensible heat and latent heat fluxes correspond very well with the observations in both magnitude and phase.