Historical evolution and future trend of meteorological drought in the upper Yangtze River basin

Climate change has exacerbated extreme weather patterns in the upper Yangtze River basin, notably amplifying the severity, occurrence, and length of meteorological droughts. These changes have significantly affected local water resources, agricultural productivity, and the regional ecosystems. This study utilized the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) to analyze the spatial and temporal trends of meteorological droughts between 1961 and 2018. Additionally, the analysis of drought characteristics was conducted using projections derived from ten separate coupled model intercomparison project phase 6 (CMIP6) simulations, based on three defined climate scenarios for the period between 2019 and 2099. Historical analysis indicates a significant temperature increase across the upper Yangtze River basin, alongside a slight rise in precipitation marked by spatial variability—northwestern areas showed increasing trends, while central regions saw declining moisture. Droughts intensified after 2000, especially in summer and autumn, with the source region and surrounding areas experiencing higher frequency and longer duration of dry conditions. Future projections suggest a transition from relatively humid to drier conditions post-2040, accompanied by a notable rise in drought events. By 2070–2099, under both moderate (SSP2-4.5) and high-emission (SSP5-8.5) scenarios, droughts are expected to intensify, with over half the period affected and some zones facing prolonged, year-round droughts.