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

Abstract

This study compares simulations from 13 CMIP5 and CMIP6 homologous models and their multi-model ensemble (MME) based on the generalized three-cornered hat method (TCH) for temperature and precipitation over the Yarlung Tsangpo-Brahmaputra River Basin (YBRB). The results showed that: (1) the MME estimations outperform the most single model, demonstrating the effectiveness of TCH in reducing model uncertainty. (2) CMIP5 and CMIP6 are more applicable for spring and autumn maximum temperatures (Tasmax), minimum temperatures (Tasmin) and precipitation in YBRB. Moreover, they showed better performance for precipitation on floodplain, for Tasmax on Tibetan Plateau, and for Tasmin in whole YBRB. (3) Relatively, CMIP5 and CMIP6 can better simulate the spatial distribution of temperature rather than precipitation (the Temporal Correlation Coefficient of Tasmax and Tasmin: 0.72 – 0.89; that of precipitation: 0.43–0.6). (4) The bias of CMIP6 for temperature and precipitation in YBRB is mostly lower than CMIP5, but still has a cold bias over YBRB (Tasmax:-7.98 °C to-14.88 °C, Tasmin:-6.24 °C to-21.45 °C) and wet bias for precipitation on Tibetan Plateau (0.56 mm-2.00 mm), dry bias on Himalayan belt (-0.69 mm to-7.56 mm) and floodplain (-0.46 mm to-6.98 mm).