中国典型城市群极端暴雨时空演化规律OA

Under the dual impacts of global climate change and rapid urbanization,extreme rainfall events exhibit pronounced non-stationarity,posing severe flood risks to densely populated regions.While prior studies have often focused on individual areas,comparative analyses across diverse climatic zones remain limited.This study investigates the spatiotemporal evolution characteristics of annual maximum 6-hour rainfall across three major Chinese urban agglomerations—the Beijing-Tianjin-Hebei(BTH)region,the Yangtze River Delta(YRD),and the Guangdong-Hong Kong-Macao Greater Bay Area(GBA)—which respectively represent typical temperate,subtropical,and tropical monsoon climates.Utilizing the GPM-IMERG high-resolution satellite precipitation dataset from 2000 to 2023,this research addresses the spatial limitations inherent in conventional rain gauge observations.A comprehensive methodological framework was employed,integrating the Mann-Kendall trend test,Pettitt change-point test,kernel density estimation(KDE),spatial gravity center trajectory analysis,and spatial heterogeneity analysis(Moran's I and Coefficient of Variation).The results reveal substantial regional disparities in extreme rainfall evolution.In terms of interannual variability,the BTH region exhibits a significant increasing trend coupled with high fluctuation and instability.Conversely,the YRD region demonstrates a state of high stability with a non-significant,slight upward drift.Although the GBA retains the highest absolute rainfall intensity,it displays a significant decreasing trend,with its stability ranking intermediate among the three regions.Regarding intra-annual distribution,a distinct latitudinal transition is observed from north to south.Seasonally,the pattern shifts from a strict unimodal regime in BTH(heavily concentrated in summer)to a mixed multi-seasonal pattern in YRD,and ultimately to a bimodal pattern(spring and summer peaks)in GBA.Diurnally,a"south-early,north-late"triggering mechanism is identified.Peak rainfall in BTH concentrates in the afternoon to late evening(14:00-21:00),driven by afternoon thermal convection,whereas peaks in YRD and GBA predominantly occur during the early morning or predawn hours(00:00-06:00),closely linked to nocturnal rain mechanisms,sea-land breezes,and low-level jets.Spatially,the gravity centers of extreme rainfall in all three agglomerations exhibit significant clustering and directional migration,shaped by local topography and prevailing wind directions.Moreover,the degree of spatial clustering and heterogeneity follows a"north-high,south-low"pattern,with inland cities generally showing stronger spatial concentration and variability than their coastal counterparts,reflecting the comparatively homogeneous spatial response of coastal plains.In summary,this study elucidates the non-stationary evolutionary mechanisms governing extreme rainfall across urban agglomerations under heterogeneous climatic backgrounds.The findings provide a robust scientific basis for optimizing regional flood control and drainage design standards,thereby facilitating the development of spatially differentiated,resilience-oriented strategies for extreme weather prevention and mitigation.