The response mechanism of urban precipitation to impervious surface expansion

Beijing Metropolitan Area Rapid urbanization has altered land‑surface characteristics, exacerbating extreme rainfall events and increasing the risk of urban flooding. However, the mechanisms by which impervious surface density (ISD)—an indicator of urban spatial structure—affects precipitation remain poorly understood, particularly across cities of different sizes. In this study, we employed XGBoost and SHAP methods to investigate the response mechanism of urban precipitation's spatiotemporal distribution to the ISD. The study reveals a significant positive correlation between impervious surface density (ISD) and annual precipitation enhancement. The effect of ISD on the increase of annual precipitation is more pronounced during the early stage of urbanization. Mechanistic analysis indicates that ISD primarily enhances precipitation through heat island effects in the initial urbanization stage, shifting to moisture transport regulation in later stage. To mitigate urban‑flooding risks driven by rapid local increases in precipitation, we recommend maintaining ISD below 47 %. These findings provide important theoretical and practical guidance for precipitation regulation and risk management in rapidly urbanizing regions worldwide. • Urban thermal effect as a key driver of local rainfall increase. • 47 % ISD thresholds play an important guiding role in the urban waterlogging. • The driving mechanism of local rainfall in city is related to ISD.