Comparison of CMIP5 and CMIP6 models for temperature and precipitation simulation over the Yarlung Tsangpo-Brahmaputra River Basin

This study compares simulations from 13 CMIP5 and CMIP6 homologous models and their multi-model ensemble (MME) for temperature and precipitation over the Yarlung Tsangpo-Brahmaputra River Basin (YBRB). The results showed that (1) the MME estimations are superior to most single models, indicating TCH is effective for reducing model uncertainty. (2) CMIP5 and CMIP6 were more applicable during spring and autumn for maximum and minimum temperatures (Tasmax, Tasmin) and precipitation over the YBRB. Moreover, CMIP5 and CMIP6 showed better performance for precipitation in the downstream floodplain, for Tasmax on the Tibetan Plateau, and for Tasmin in the whole YBRB. (3) CMIP5 and CMIP6 can better simulate the spatial distribution of temperature rather than precipitation (temporal correlation coefficient (TCC) of Tasmax and Tasmin: 0.72-0.89; TCC of precipitation: 0.43-0.6). Both perform poorly in simulating interannual variation in temperature and precipitation (all anomaly correlation coefficients (ACC) <0.60). (4) The bias of CMIP6 for temperature and precipitation is mostly lower than CMIP5, but still has a cold bias over YBRB (Tasmax: -7.98 to -14.88 degrees C, Tasmin: -6.24 to -21.45 degrees C) and wet bias on Tibetan Plateau (0.56-2.00 mm), dry bias on Himalayan belt (-0.69 to -7.56 mm), and floodplain (-0.46 to -6.98 mm).