Multiscale spatiotemporal impacts of urbanization on warm-season precipitation across Chinese urban agglomerations

Urbanization has been widely shown to modify precipitation, yet it remains unclear how urbanization-induced precipitation changes vary jointly across temporal scales, spatial hierarchies, climate regimes, and precipitation intensities. Here, we used high-resolution IMERG hourly precipitation data from 2001 to 2024, dynamic Global Urban Boundaries, and a multiscale urban–rural comparison framework to quantify urbanization effects on warm-season precipitation across 20 major Chinese urban agglomerations (UAs) and 61 representative cities. Our results show that urbanization strongly enhances light-to-moderate precipitation, with more than 90% of UAs exhibiting positive urban effects and 75%–90% showing statistically significant ( p < 0.05) increases for light precipitation. However, this enhancement weakens with increasing precipitation intensity, and approximately 60% of UAs exhibit negative urban effects for extreme precipitation. The urban effect also varies markedly across climate zones. For light-to-moderate precipitation, the mean urban effect in humid regions is more than twice that in arid regions, whereas this gradient reverses for extreme precipitation, with stronger urban-induced suppression in humid and continental regions. Temporally, urbanization-induced increases are more evident at the hourly than daily scale: 75%–100% of UAs show stronger hourly effects for light-to-moderate precipitation, and in 55%–60% of UAs the hourly effect exceeds the daily effect by more than a factor of two. Diurnal analysis further reveals that more than 40% of UAs experience day–night sign reversals in the urban effect on extreme precipitation. Spatially, UA-scale and city-level responses are highly consistent for light-to-moderate precipitation, with more than 70% of city–UA pairs sharing the same sign, but this consistency declines to approximately 50% for extreme precipitation. These findings demonstrate that urbanization does not uniformly intensify precipitation; instead, it redistributes precipitation changes across intensity classes, temporal scales, and spatial hierarchies. Our results highlight the need to consider sub-daily processes and city-level heterogeneity when assessing urban hydroclimatic risks in rapidly urbanizing regions.