High-resolution regional climate projections over South Asia

We generate an ensemble of regional climate projections over the South Asian monsoon region using multiple global climate models' (GCMs) output from Coupled Model Intercomparison Project Phase 5 (CMIP5) archives and two regional climate models (RCMs); RegCM4 and WRF. Each ensemble member consists of 30 years in the baseline period (1976-2005) and 45 years in the near-term future period (2006-2050) under the Representative Concentration Pathway (RCP) 8.5. Both RegCM4 and WRF are run at 18 km horizontal grid spacing with 18 and 27 levels in the vertical respectively. We focus our analysis on the summer monsoon period, including inter-annual and intra-seasonal summer monsoon variability. In addition, we investigate the effect of increase in greenhouse gas forcing on the monsoon dynamics, onset and persistence. Use of a multiple RCM-GCM modeling framework allows us to explore the relative role of RCMs' internal dynamics versus boundary conditions provided by GCMs in high-resolution regional climate projections. In addition, the use of a higher resolution in regional models simulations allows us to understand the role of mesoscale monsoon dynamics in shaping the local precipitation response to the large scale climate forcing. In particular, we compare the projections from RCMs with those from GCMs to understand how uncertainty in GCMs' projections propagates through RCMs, e.g., the sign and spread of precipitation change.