2010年7月18-20日西南低涡东北上影响华北，造成了华北地区大范围大暴雨过程。本文利用NCEP/NCAR 1º×1º再分析场资料，分析了本次西南涡北上加强的原因和造成河北大暴雨的形成机制。结果表明：西南涡是这次华北暴雨的主要影响系统，暴雨的持续与西南涡和中纬度高空槽（低涡）的耦合过程密切相关；高、低空急流相互作用，有利于低层上升运动的发展和加强；高空湿位涡扰动下传，使得西南低涡发展加强；暴雨发生时，其上空正涡度中心和强散度中心相耦合，强的上升运动对低层水汽辐合抬升产生暴雨十分有利；中低层的高能高湿为低涡的发展和暴雨的维持提供了能量和水汽。%Due to the effect of the southwestern low vortex, a heavy precipitation in North China during 18 to 20 July 2010 occurred. Using NCEP/NCAR reanalysis data, the physical mechanism of the heavy rainstorm processes are diagnostically analyzed. The main conclusions are as follows. The rainstorm process is mainly affected by southwestern low vortex, the coupling interaction between mid-latitude upper trough and southwestern vortex leads to the development of the rainstorm. The low-rise was caused by the interaction between upper and lower jets, and the downward spread of moist potential vorticity is also of an advantage to the development of the southwest vortex; The positive vorticity and the center of divergence lead to the low-level moisture convergence for the rainstorm. The high energy and high humidity in middle and low level air provides energy and water vapor, which is very important to strengthen the southwestern vortex and keep the rainstorm continuously.
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