"25.7"北京致灾性暴雨的精细化特征及大尺度环流异常OA

In late July 2025,Beijing experienced a prolonged and disastrous rainstorm event(hereafter referred to as the"25.7"event),which caused severe economic losses and casualties.Using high-resolution precipitation observations from national and regional meteorological stations in Beijing during 1961-2025,this study examines the refined characteristics of this extreme rainfall event and investigates the associated large-scale anom-alous circulation background and moisture transport mechanisms.The results show that the"25.7"event occurred against a background of anomalously wet summer conditions and an earlier-than-normal onset of the rainy season in Beijing,with a marked increase in regional heavy precipitation events since 2010.During the event,the city-wide mean accumulated precipitation reached 211.1 mm.The Miyun station recorded its highest rainfall since 1961(366.6 mm),while a local maximum of 574.3 mm was observed at the Langfangyu station.Notably,the duration of continuous precipitation over Beijing reached 147 h,exceeding the historical record set during the"63.8"event in 1963.At the Miyun station,heavy rainfall persisted for approximately 106 h,with rainfall inten-sity exceeding 20 mm·h-1 for 42 h.Compared with other major rainstorm events since 2010,the"25.7"event ranks among the most extreme in terms of mean rainfall amount,duration and local maxima.Circulation analyses reveal that during the summer of 2025,the 500 hPa geopotential height anomaly field over the mid-high latitudes of Eurasia exhibited a pronounced"negative-positive-negative"teleconnection wave train,whose energy disper-sion and persistent intensification provided a favorable large-scale background for extreme precipitation.Concur-rently,the western Pacific subtropical high(WPSH)was stronger and positioned farther north than climatology,with its western ridge line remaining north of 35°N in late July.Together with a significantly enhanced East Asian summer monsoon,these conditions established an efficient moisture transport pathway toward northern China.During the"25.7"event,a deep trough was located near Lake Baikal at 500 hPa level,placing the Beijing-Tian-jin-Hebei region ahead of the trough.The northern boundary of the WPSH extended anomalously to approximately 40°N,and a strong southeasterly low-level jet developed between the WPSH and the low-pressure system to its north.In addition,Typhoons Francisco and Co-may further intensified and sustained the moisture transport along the southeastern pathway toward Beijing.The combined effects of these circulation features ultimately led to this record-breaking,long-lasting,and extreme rainfall event.