Attribution of the most severe decadal drought in Southwest China during 2003–2014 and its impact on vegetation productivity

Study region Southwest China (SWC). Study focus This study identifies the decadal drought background of frequent droughts in SWC since the early 21st century, quantifies the roles of precipitation and potential evapotranspiration (PET), and evaluates vegetation impacts. Monthly precipitation and PET during 1961–2023 were used to calculate the 12-month Standardized Precipitation Evapotranspiration Index (SPEI12). An objective change-point test, quantitative attribution, moisture budget analysis, and vegetation productivity indicators were combined. New hydrological insights for the region The most severe decadal drought in SWC occurred during 2003–2014, characterized by a 12-month cumulative precipitation deficit of 49.34 mm and an increase in PET of 32.18 mm. Precipitation decline was the dominant contributor to the decadal drought, accounting for 68.6% of its intensity, while enhanced PET further intensified drought severity, with residual PET and precipitation-associated PET contributing 20.9% and 10.5%, respectively. About 70% of the precipitation deficit occurred during the wet season. Moisture budget analysis reveals a clear hydrological pathway linking wet-season precipitation decline to atmospheric circulation. Anomalous descending motion weakened vertical moisture transport, with dynamic vertical moisture advection reaching −0.35 mm day⁻¹, thereby enhancing moisture divergence and reducing wet-season precipitation over SWC. The persistent water deficit was accompanied by a nonlinear reduction in vegetation productivity under moderate-to-extreme drought conditions, with the strongest impacts in Yunnan, Guangxi, and the Sichuan–Chongqing–Guizhou border region.