Issues of Soil Moisture Coupling in MM5: Simulation of the Diurnal Cycle over the FIFE Area

Abstract

This study evaluates the issues of soil moisture coupling on the partitioning of surface fluxes at the diurnal timescale over a mesoscale domain from the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) in Kansas. A state-of-the-art atmospheric model (the Fifth-Generation Pennsylvania State University?National Center for Atmospheric Research Mesoscale Model, or MM5) is used as a control run in which soil moisture is prescribed by a time-invariant as well as time-varying moisture availability function. Then, in a coupled model simulation, the atmospheric model is coupled with a detailed land surface model. Three days are simulated with progressively smaller surface soil moisture conditions to identify the influence of interactive soil moisture on surface fluxes partitioning at the diurnal timescale. Preliminary results suggest that, for days with wetter surface soil moisture conditions and moderately high wind speed, a time-variant interactive soil moisture representation provides a more accurate partitioning of surface fluxes. For drier surface conditions with relatively low wind speed, a constant soil moisture availability function may be adequate.