A Demonstration of the Value of Nudging in Downscaled Regional Climate Simulations from a Global Climate Model

The use of nudging for downscaled regional climate simulations has been somewhat controversial over the past several years but has recently been gaining popularity. Several recent studies that have used reanalysis (i.e., verifiable) fields as a proxy for global climate model (GCM) input have shown that nudging can be beneficial toward achieving the desired downscaled fields. In this study, the value of nudging will be shown using GCM fields from the NASA/GISS ModelE that are downscaled using the Weather Research and Forecasting (WRF) Model as a regional climate model (RCM). Several different methods of nudging are explored in year-long simulations. It will be shown that nudging can be used to generate downscaled fields that allow the large-scale features from the GCM to be recast by the RCM and still allow the RCM to generate plausible mesoscale features. In addition, it will be shown that the method of nudging and the choices made with respect to how nudging is used in the RCM are extremely critical to balance the constraint of the GCM against the freedom of the RCM to develop its own fields.