Evaluation of the Effects of Land Surface Processes on Convective Precipitation Using a Nonhydrostatic Version of the NCEP Eta Model

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9612388 Gallus The U.S. Weather Research Program (USWRP) is an interagency activity designed to perform and implement the research necessary to improve the delivery of weather services to the nation. Under this Program, the National Science Foundation and the National Oceanic and Atmospheric Administration are jointly evaluating and supporting research of high priority to the USWRP. Variations in earth surface properties, such as differential heating and soil moisture, are known to have a significant impact on numerical weather forecasts. The Principal Investigator will evaluate the impact of land use and soil moisture on mesoscale precipitation systems simulated with a high-resolution nonhydrostatic version of the National Oceanic and Atmospheric Administration s National Center for Environmental Prediction (NCEP)'s Eta model. In particular, the role of surface heat and moisture fluxes in preconditioning the thermodynamic environment and the dynamical effects of boundary-layer circulations caused by surface inhomogeneities will be investigated, focusing on orographic and frontal forcing of precipitation. The nonhydrostatic Eta model will be run over a 24-48 hour time period both for historical cases and in an operational-like mode. Historical cases will be chosen where orography, frontal forcing or local mesoscale convection resulted in unique precipitation systems whose scales were small enough that nonhydrostatic dynamics can be assumed to be important. Initialization and verification of historical cases can be aided by incorporating archived hourly precipitation data. The operational- like mode of the project will rely upon the operational initialization and verification procedures used at NCEP. Results of the research will contribute to (i) improving our understanding of the effects of land use and soil moisture on small-scale precipitation systems, and (ii) testing and refinement of the nonhydrostatic Eta model, which is planned to be primary short-range forecasting tool of the future at NCEP. ***