High-Resolution Dynamic Downscaling of Winter Climate over the Himalaya

Abstract

Observed climate data are few over the inaccessible regions of the Himalaya which limits the understanding of climate variability of this third pole. Therefore, dynamic downscaling methods need to be employed to obtain dynamically consistent high-resolution climate information over the Himalaya. In this study, dynamic downscaling simulations have been described that were obtained using a regional climate model (RegCM4) and the high-resolution WRF model. The WRF model was used to downscale observed coarse-resolution ERA-I data from 1991 to 2010. The RegCM4 used the hindcasts from a coarse resolution General Circulation Models (GCM) from 1982 to 2009. From the Weather Research and Forecast (WRF) model simulations, it was found that snowfall contributes to about 80% or more amount of total precipitation over the western Himalaya. Detailed vertical structure of circulation and temperature could be deciphered using the WRF model, especially during excess and deficit years of precipitation. Detailed examination of cloud microphysical processes shows that while the rain water confines to only lower levels, snow has maximum magnitude among all the hydrometeors during excess precipitation years. The RegCM4 model could simulate better skill in precipitation hindcasts than the GCM used to force it.