Urbanization reshapes extreme precipitation metrics in typical urban agglomerations of Eastern China

A deeper understanding of the impact of urbanization on hourly extreme precipitation is essential for building sustainable and resilient urban environments. In this study, we used a high-resolution land cover dataset and long time series of hourly precipitation observations to assess the impact of urbanization on long-term trends and diurnal patterns of hourly extreme precipitation in typical urban agglomeration regions of eastern China, during the warm season of 1978-2021. The results showed that eastern China experienced an overall increase in hourly precipitation, while the intensity trends were 0.06 mm/h/decade and 0.03 mm/h/decade for urban and rural areas, respectively. Urban areas more likely to experienced strong precipitation with short duration, but urbanrural differences in extreme precipitation showed obvious regional characteristics. The difference in extreme precipitation intensity between urban and rural areas increased in the regions of the lower Yangtze River (LYR) valley, Sichuan Basin and southern China, but decreased in northeast China and Beijing-Tianjin-Hebei (BTH) regions. For the diurnal cycle, extreme precipitation enhancement in urban areas occurred mostly at peak hours. Urban stations had higher hourly extreme precipitation intensity than rural stations throughout the diurnal cycle, with the maximum difference of 1.79 mm/h occurring at 16:00 LST. It found that extreme precipitation amount and intensity in urban areas increased with urban heat island (UHI) effect, and UHI indeed plays an important role in the convective initiation and strengthening of local extreme precipitation.