Abstract: To reveal the change trend and evolution patterns of future drought during 2020-2099 in the middle and lower reaches of the Yangtze River Basin, we calculated the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) based on precipitation and potential evapotranspiration (PET) data from 4 Global Climate Models (GCMs) under RCP-2.6,RCP-6.0 and RCP-8.5 scenarios, which are derived from Inter-Sectoral Impact Model Inter-comparison Project (ISIMIP). We also looked into the performance of SPI and SPEI in detecting and depicting drought features. Results unveil an overall climbing trend of SPI in future, with the Hanjiang River basin and the northwest Dongting Lake network witnessing a surge, which means that drought in these regions will relieve obviously in the future. SPEI shows a reducing trend in most regions under all scenarios, and such reduction escalates with the rising of emission concentration; particularly, in the southeast of Dongting Lake network and Poyang Lake network,the reductions are larger than that in other regions,implying a notable drying trend in future.SPEI drops greater in regions where SPI declined under all scenarios.The correlation between SPI and SPEI gradually intensifies from north to south and from west to east in the study area.The overall correlation between SPI and SPEI weakens gradually from RCP-2.6,to RCP-6.0 and to RCP-8.5 scenario.

Key words: drought patterns, space-time evolution, SPI, SPEI, ISIMIP, middle and lower reaches of the Yangtze River Basin