Selection and Classification of Warm-Sector Rainfall Events in Beijing-Tianjin-Hebei

Based on hourly precipitation data, the warm-sector rainfall events in Beijing-Tianjin-Hebei region are selected and classified using objective methods. There are 33 warm-sector rainfall events in this region from 2010 to 2023. They mainly occur during June and August with the most in July. The average lifetime of these warm-sector rainfall events is 5.44 h. The warm-sector rainfall events are mainly concentrated in the center of the Beijing-Tianjin-Hebei region, and the frequency of occurrence in the east is higher than that in the west. The frequency of occurrence in Beijing is much higher than that in other regions, and it is mainly concentrated in the terrain bell mouth of northeast Beijing. According to the circulation situation that generates warm-sector rainfall, three types of precipitation are obtained: low-vortex type, shear-line type and southerly-wind type. The occurrence months, starting times and locations of warm-sector rainfall events in different types are slightly different. Based on the analysis of the synthetic circulation situation, the dynamic, water vapor and low-level vertical motion conditions of the low-vortex type is most favorable for warm-sector rainfall. The vertical upward movement of shear line warm-sector rainfall events is strong in Beijing; The dynamic condition of southerly-wind type is the weakest, but the water vapor condition is more favorable and the occurrence is related to the topographic distribution of  Beijing-Tianjin-Hebei.