Characterizing spatiotemporal dynamics of hourly extreme precipitation in China with an adaptive 3D clustering approach

Study region China, spanning the East Asian monsoon region and its northwestern inland transition zones, where extreme precipitation events (EPEs) show strong spatial heterogeneity and pose substantial hydrological-disaster risks. Study focus This study investigates the spatiotemporal evolution characteristics and propagation patterns of EPEs across China during 1985–2024. The central objective is to move beyond station-based, two-dimensional, or daily-scale descriptions and reconstruct complete precipitation-system trajectories in a continuous three-dimensional space. To achieve this, an adaptive 3D spatiotemporal clustering framework based on 3D-DBSCAN was developed and applied to ERA5 hourly precipitation data. Extreme precipitation grids were mapped into a standardized longitude-latitude-time space, while k-distance-based parameter optimization and physical constraint filtering were used to reduce subjective parameter selection and avoid artificial fragmentation of fast-moving or intermittent events. Precipitation-weighted centroids were then used to quantify event movement distance and direction, and to classify typical propagation patterns. New hydrological insights for the region The framework identified independent EPEs and revealed five dominant propagation patterns. EPEs in China show a clear northwestward movement preference, whereas southward events are infrequent and spatially limited. Northwestward events, especially ultra-long-distance events, exhibit the greatest hydrological extremeness, with longer durations, larger affected areas, and higher cumulative magnitudes. These trajectories indicate a regional “westward shift and northward leap” of extreme-rainfall activity, linked to the East Asian summer monsoon, western Pacific subtropical high, and mid-latitude westerlies.