Evaluation of high-resolution simulations of temperature and precipitation extremes over the United States

Extreme climate events have been increasing over much of the world, and dynamical models predict further increases in response to enhanced greenhouse forcing. We examine the ability of a high-resolution nested climate model, RegCM3, to capture extreme temperature and precipitation events over the conterminous United States, using high-quality observational and reanalysis data for comparison. Our analyses reveal that RegCM3 captures the pattern of mean, interannual variability, and trend in extreme temperature and precipitation events. However, consistent biases do exist, including wet biases in the topographically-complex regions of the western United States and hot biases in the southern and central United States. The biases in extreme precipitation in the western United States are associated with excessively strong surface and low- level winds. The biases in extreme temperature and precipitation in the southcentral United States are at least partially driven by biases in circulation and moisture fields in RegCM3. Our evaluation should enable more informed application and improvement of high-resolution climate models for the study of future changes in socially- and economically-relevant extreme events.