CALIBRATION OF SOIL-MOISTURE FOR LARGE-EDDY SIMULATIONS OVER THE FIFEAREA

A case day, 11 October 1987, was chosen for simulation using the Regio nal Atmospheric Modeling System (RAMS). The day was unique from other ''golden'' days of the First International Satellite Land Surface Clim atology Project (ISLSCP) Field Experiment (FIFE) in that the surface w ind speeds were light in terms of magnitude. Numerous datasets were us ed to initialize the meteorology, vegetation, canopy height, roughness length, topography, and soil properties. The simulation was performed using the RAMS nested grid feature. First, the large-scale flow repro duced by RAMS was evaluated against the observations taken during FIFE and archived data avaiiable at the National Center for Atmospheric Re search. Next, a large-eddy simulation (LES) was integrated for a 6-h p eriod starting at 1500 UTC 11 October 1987. FIFE surface flux and surf ace thermodynamic and dynamic data were then used to evaluate the LES. It was found that LES fluxes were in poor spatial agreement with the observations, although domain-averaged values were in good agreement. A technique far initializing the near-surface to surface soil moisture was then developed after finding a near-Linear relationship between 6 -h averaged latent heat and the initial model-gridded soil moisture ob tained from an objective analysis of field data. The LES was performed again using the new soil moisture obtained from the relationship. The evaluation showed significant improvement in the model's ability to r epresent spatial heterogeneity of surface fluxes present on 11 October 1987.