Statistical Downscaling of Daily Temperatures and Precipitation Data from Coupled Model Inter-comparison Project 5 (CMIP5)-RCPs Experiment: In Weyib River Basin, Southeastern Ethiopia

Impact of climate change on the temperature and precipitation characteristics of Weyib River basin in Ethiopia has been investigated using CanESM2 model for the RCP2.6, RCP4.5, and RCP8.5 scenarios. The statistical downscaling model calibrated and validated using the observed daily data of 12 meteorological stations was used to generate the future scenario. The change in mean annual maximum temperature from the base period has indicated an increment of 0.16, 0.14, and 0.15 °C for RCP2.6, 0.12, 0.19, and 0.21 °C for RCP4.5, and 0.12, 0.22 and 0.32 °C for RCP8.5 for the 2020s, 2050s, and 2080s, respectively. Mean annual minimum temperature has shown an increment of 0.30, 0.43, and 0.39 °C for RCP2.6, 0.31, 0.48, and 0.57 °C for RCP4.5, and 0.34, 0.66 and 1.04 °C for RCP8.5 for the 2020s, 2050s and 2080s, respectively. For the percentage change in mean annual precipitation from the base period, the increment has been 8.68, 12.93, and 11.34% for RCP2.6, 9.54, 14.36, and 16.94% for RCP4.5, and 14.70, 19.14, and 28.69% for RCP8.5 for the 2020s, 2050s, and 2080s, respectively. There was a significantly (at 5% significant level) increasing trend of both temperatures and precipitation in all the three RCPs for future until the year 2100. The increment of rainfall in the study area was comparatively higher in the dry season 20.68% in the 2020s, 33.65% in 2050s, and 53.74% in 2080s for RCP8.5 which might have positive impact on pastoral region of the study area and it might affect the highland areas negatively since this season is expressly main crop harvesting period.