Extreme precipitation revealed through high-resolution dynamical downscaling

Here we will describe our use of high-resolution dynamical downscaling as a means to simulate the regional climate, variability, and projected changes in short-duration extreme precipitation events. Our basic approach differs from a traditional regional climate model application in that it involves a sequence of daily integrations. We use the Weather Research and Forecasting (WRF) model, with horizontal grid lengths of several kilometers to allow for explicit representation of deep convective storms and hence a compilation of their associated rainfall statistics over a large portion of the conterminous United States. Reanalysis-driven sequences of WRF model integrations yield precipitation with a realistic geographical distribution and otherwise with a diurnal cycle that is consistent with observations. Moreover, the occurrence frequency of short-duration, heavy-precipitation events similarly compares well to analyses of hourly rain gauge data. These historical simulations will be compared with GCM-driven simulations, to describe projected changes in precipitation extremes over the late 21st Century.