Projection of Summer Rainfall in the Yangtze River Basin in the Next 30 Years under Different Shared Socioeconomic Pathways

Based on the historical experiments of Coupled Model Intercomparison Project Phase 6 (CMIP6), 22 models are systematically evaluated by comprehensive rating metrics (MR). Later, ten models (GFDL-CM4, EC-Earth3, MIROC6, etc.) with reliable performances are chosen to project summer rainfall in the Yangtze River basin in the next 30 years (2021–2050) under SSP245 and SSP585. The results suggest that compared with 1981–2010, the total rainfall amount (PRCPTOT) and rainfall intensity (SDII) are projected to increase, with a large increase in the upper plateau and the middle-lower plains. Conversely, the occurrence of rainfall (R1mm) changes a little due to an opposite signal in the upper and middle-lower reaches. The heavy rainfall (R95p) is projected to increase by 9.6% and 16.5%, and extreme rainfall (R99p) is projected to increase by 10.2% and 15.5% for SSP245 and SSP585, respectively. The maximum 5-day rainfall (RX5day) also exhibits a pronounced change. Besides, the maximum consecutive dry days (CDD) will increase, especially in the upper reaches. For different SSPs, the changes in SSP585 are greater than those in SSP245, indicating more rainfall amount and more occurrences of heavy-extreme rainfall events, as well as a larger potential increase of droughts. The increasing risk of extreme rainfalls and floods in the middle and lower reaches and drought in the upper reaches particularly deserve greater attention.