Asymmetric Impacts of Urbanization on Extreme Hourly Precipitation Across the Yangtze River Delta Urban Agglomeration During 1978–2012

Significant progress has been made in understanding how extreme precipitation responds to climate warming across various time scales. However, the impact of urbanization on these events remains unclear. This study aims to thoroughly examine the effects of urbanization on extreme hourly precipitation (EHP) and its spatial heterogeneity based on dynamic station classification methods and various EHP indices using high-resolution records of hourly precipitation in the Yangtze River Delta (YRD) urban agglomeration. We also explore how urbanization has contributed to changes in extreme precipitation and the associated uncertainties. The results indicate an overall increase in all EHP indices across the YRD, with significant increases being more pronounced in urban areas. Furthermore, the changes in the EHP correlate positively with urbanization, showing greater increases at higher levels of urbanization. While the impact of urbanization on the EHP changes cannot be overlooked, its contribution appears relatively limited, with the contributions being less than 50%. The effects of urbanization on precipitation changes are predominantly positive, with noticeable spatial heterogeneity for different sub-regions and temporal variations during various stages or levels of urbanization. Moreover, urbanization effects and contributions are influenced by the urban–rural classification methods, especially regarding their contributions.