The Influence of Watershed-scale Dynamic Soil Moisture on Local PBL Evolution and Structure: Modeled versus Observed

From August 18-23, 1994 an Intensive Observation Period (IOP)of the NASA/USDA field experiment Washita '94 was conducted in the nearly 600 square kilometer Little Washita Watershed (LWW) in southwest Oklahoma. During this period, 3-hourly atmospheric sounding data was collected from 6 AM local time to 6 PM local time. In addition, daily gravimetric soil moisture samples and half-hourly surface flux and meteorological data were collected.

We have applied and validated the watershed scale land surface parameterization TOPLATS to simulate temporally and spatially varying soil moisture and surface fluxes during this period. TOPLATS is coupled to a 1-dimensional column version of the non-hydrostatic PSU/NCAR MM5, configured with a 1.5 order TKE boundary layer scheme, the Kain-Fritch deep convection scheme, an explicit moisture scheme and the Dudhia radiation scheme. MM5-1d has been run both continuously and on a day-by-day basis for the entire IOP. By comparing the modeled and measured thermodynamic profiles as well as profiles modeled when the default MM5 "SLAB" LSP (without dynamic soil moisture) is used, we will demonstrate the marked improvement in simulated profiles from TOPLATS relative to SLAB. In addition, by comparing TKE and kinematic flux profiles generated using TOPLATS versus SLAB, we will describe the mechanisms by which the variable soil moisture affects local boundary layer structure and development.