Noah LSM surface layer formulations used in the operational mesoscale NAM (WRF-NMM) model

The Noah land-surface model (LSM) is unified among several operational and research groups (i.e. NCEP, NCAR, AFWA), and is one of the primary land-surface options in the mesoscale Weather Research and Forecasting (WRF) model that will be used as the operational North American Mesoscale (NAM) modeling system at NCEP in 2006. Recent success with upgrades to cold season processes, refinements to vegetation and soil parameters, the addition of surface emissivity, and other changes in the Noah LSM have been tested in the coupled setting of the NAM model. Here we further examine the surface layer parameterization necessary in the calculation of surface fluxes, specifically the formulations for surface roughness (for heat, moisture, and momentum) and the stability-dependent profile functions. These formulations use the assumption of local similarity theory and can be explicitly or implicitly-based, but must also account for model terrain and grid-box size, and flow-dependent and intermittent (e.g. stable boundary layer) turbulence issues, all of which affect the choice of formulations used.