Water Vapor Transport Characteristics of the Extreme Precipitation Event in Liaoning in July 2024

2024年7月24日至26日辽宁出现极端强降水，暴雨覆盖面积近71%，其中沈阳地区累计降水量556.6 mm，为1951年以来最强降雨。文章利用欧拉方法分析水汽输送、辐合特征与局地水汽收支，利用拉格朗日方法追踪水汽来源并量化。结果表明：东北冷涡、台风“格美”、副高共同作用为暴雨的发生和维持提供了有利的环流背景，该形势的稳定维持是降水长时间持续的原因；南边界水汽输送量对降水增大起到关键作用，辽河流域形成的强水汽辐合中心为极端降水创造了有利条件，上升运动与深厚的湿层有利于高效降水；不同高度水汽来源存在差异，700 hPa来自南海、西太平洋、内陆的水汽贡献率相近，850 hPa来自西太平洋的水汽贡献率总计85.7%，南海占比14.3%；850 hPa各水汽通道均受到台风影响，台风外围水汽输送占比49.3%。From July 24 to 26, 2024, Liaoning experienced extreme heavy rainfall, with the area affected by torrential rain covering nearly 71%. The cumulative precipitation of Shenyang reached 556.6 mm, marking the strongest rainfall since 1951. This article analyzes the moisture transport, convergence characteristics, and local moisture budget using the Eulerian method, and traces and quantifies the sources of moisture using the Lagrangian method. The results indicate that the combined influence of the Northeast cold vortex, Typhoon Gaemi, and the subtropical high created a favorable circulation background for the occurrence and persistence of the heavy rain, with the stable maintenance of this pattern being the reason for the prolonged duration of precipitation. The moisture transport from the southern boundary played a crucial role in increasing precipitation, and the strong moisture convergence center formed in the Liaohe River basin created favorable conditions for extreme rainfall. Upward motion and a deep moist layer facilitated efficient precipitation. There were differences in moisture sources at different altitudes: at 700 hPa, the contributions of moisture from the South China Sea, the Western Pacific, and inland areas were similar; while at 850 hPa, the contribution of moisture from the Western Pacific accounted for a total of 85.7%, while the South China Sea accounted for 14.3%. All moisture channels at 850 hPa were influenced by the typhoon, with moisture transport from the typhoon’s periphery accounting for 49.3%.