Abstract: This paper presents a systematical analysis on the trends in the hourly-scale extreme precipitation in Beijing from 2000 to 2023 under the influence of urban heat islands and urbanization, based on the observation data of high-resolution precipitation, surface temperature, and impervious surface coverage. To achieve a comprehensive analysis, we use multiple statistical and spatial analysis methods－including trend testing, change point detection, L-moment analysis, cluster analysis, and space-time cube and emerging hot spot analysis. The results indicate a significant overall increase in extreme precipitation. The urbanizing process underwent a structural shift in 2011, leading to an elevated risk of extreme precipitation. High-value precipitation areas are primarily distributed in the city’s southwestern part, while the regions with strong variability and extreme intensity are concentrated in the transitional zones between the urban core and the western and northern mountainous areas. The spatiotemporal patterns of urban heat island are characterized by a stable core and active periphery, closely related to that of the extreme precipitation. Combination of ongoing urbanization and intensifying heat island effects has intensified hourly-scale extreme precipitation in Beijing, increasing spatial heterogeneity and complexity in associated risks.

Key words: extreme precipitation, hourly scale, urbanization, urban heat island effect, L-moment analysis, emerging hot spot analysis