Fine-scale spatiotemporal distribution characteristics of precipitation in the Dabie Mountains Region

Based on the hourly rainfall data obtained from 1,491 gauge stations from 2009 to 2021, this study examined the fine-scale spatiotemporal patterns of warm-season (May to September) precipitation in the Dabie Mountains (DBM) within the Yangtze River Basin. Our main findings are as follows. (1) The precipitation in the DBM exhibits pronounced spatial heterogeneity, with significantly higher rainfall amount and frequency observed at mountain peaks and northeastern slopes compared to surrounding plains. Two regions of high rainfall intensity were located on the southeastern slopes and in a valley on the southwestern slopes. (2) A total of 208 Long-Duration-Large-Coverage (LDLC) rainfall events were identified. Based on the centroid locations of the accumulated precipitation for each event, LDLC events were objectively classified into four types: Northwest-type (67 events), Northeast-type (16 events), Southwest-type (83 events), and Southeast-type (42 events). (3) The interaction between wind and terrain fundamentally modulates precipitation distribution: Northwest-type (terrain-crossing southwesterlies), Northeast-type (cyclonic circulation over northeastern slopes), Southwest-type (orographically blocked southwesterlies), Southeast-type (eastward-displaced southwesterlies maximum relative to Southwest-type). (4) The diurnal variation of warm-season rainfall amount in the DBM exhibits a bimodal distribution, with peaks occurring in the early morning (0700–0900 LST) and afternoon (1500–1600 LST). During the afternoon, precipitation occurs more frequently at higher elevations than in lowland areas due to thermally forced convergent anomalies over mountain peaks. Overall, these findings provide a refined comprehension of the spatiotemporal patterns of rainfall in the DBM.