Quantifying the urbanization influences on intensifying extreme precipitation from 1971 to 2023 over the Yangtze River Delta in East China

Introduction Extreme precipitation exerts serious impacts on human livelihood and ecological systems with global climate change and rapid urbanization. While the quantitative evaluation of regional urbanization influences on extreme precipitation change is still limited. Methods This study investigates the long-term variations in extreme precipitation indices (EPIs) over the Yangtze River Delta (YRD) during 1971–2023 and quantitatively assesses the contribution of urbanization using a dynamic urban-rural station classification based on the time-varying impervious area proportion (IAP) dataset. Results The results suggested that: (1) most EPIs exhibited significant increasing trends across the YRD, characterized by significant increase in both intensity indices (6.6–43.2 mm decade −1 ) and frequency indices (0.08–0.84 days decade −1 ); (2) Urbanization enhances extreme precipitation more strongly at urban stations, contributing approximately 20.8% and 26.3% to the increase in intensidy and frequency indices, respectively. At the seasonal scale, urbanization exerted pronounced enhancement effects on most EPIs in summer and autumn but weakening effects in the spring and winter; (3) Urbanization effects strengthen with increasing urbanization level, with highly urbanized areas showing markedly larger increases in R90pTOT and R95pTOT (4.39 and 4.15 mm decade −1 ), confirming the non-uniform, level-dependent nature of urbanization’s influences on extreme precipitation regimes. Dicussion This study is anticipated to provide valuable insights for urban landscape planning and the mitigation of adverse impacts arising from extreme climate events in urban areas.