摘要：Understanding the driving factors for precipitation extremes matters for adaptation and mitigation measures against the changing hydrometeorological hazards in Yangtze River basin, a habitable area that provide water resources for domestic, farming and industrial needs. However, the region is naturally subject to major floods linked to monsoonal heavy precipitation during May-September. This study aims to quantify anthropogenic influences on the changing risk of two-week long precipitation extremes like the 2019 July extreme cases, as well as events of shorter durations, over the middle and lower reaches of Yangtze River basin (MLYRB). Precipitation extremes with different durations ranging from 1-day to 14-day maximum precipitation accumulations are investigated. Gridded daily precipitation based on nearly 2,400 meteorological stations across China are used to define maximum accumulated precipitation extremes over the MLYRB in July during 1961-2019. Attribution analysis is conducted by using the Met Office HadGEM3-GA6 modelling system which comprises two sets of 525- member ensembles for 2019. One is forced with observed sea-surface temperatures (SSTs), sea-ice and all-forcings and the other is forced with pre-industrialized SSTs and natural forcings only. The risk ratio between the exceedance probabilities estimated from all-forcing and natural-forcing simulations is calculated to quantify the anthropogenic contribution to the changing risks of the 2019 July-like precipitation extremes. The results reveal that anthropogenic warming has reduced the likelihood of 2019-like 14-day heavy precipitation over the mid-lower reaches of the Yangtze River by 20%, but increased that of two-day extremes by 30%.
