Future Climate Projections using the LARS-WG6 downscaling model over Upper Indus Basin, Pakistan

Abstract

This study investigates the projections of precipitation and temperature at local-scale in the Upper Indus Basin (UIB) in Pakistan using six Regional Climate Models (RCMs) from CORDEX, under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5). For twenty-four stations spread across the study area, the daily data from the six different RCMs for maximum temperature (Tmax), minimum temperature (Tmin) and precipitation(pr) at a spatial resolution of 0.44o was downscaled using Long Ashton Research Station Weather Generator, version six (LARS-WG6). Investigations were made to predict changes in mean annual values of Tmax, Tmin and precipitation during two future periods, i.e., the mid-century (2041–2070) and end-century (2071–2100). Model results from statistical and graphical comparison validated that the LARS-WG6 is capable of simulating both the temperature and the precipitation in the UIB. Each of the six RCMs and their ensemble revealed a continuous increased temperature projections in the basin; nevertheless, there is variation in projected magnitude across RCMs and between RCPs. In general, the rise in average Tmax and Tmin was found to be greater under RCP 8.5 than RCP 4.5 possibly due to unmitigated greenhouse gas emissions (GHGs). The precipitation projections follow nonuniform trend. i.e., not all RCMs agree whether the precipitation will increase or decrease in the basin and no orderly variations were detected during any of the future time periods under any RCP. However. an overall increase in precipitation is projected by the ensemble of RCMS.