华北地区一次区域性暴雨天气分析

Synoptic Diagnosis of a Rainstorm Event on August 31 2015 in North China

本文运用常规天气资料及NCEP1°×1°间隔6h再分析资料，采取天气学诊断方法，从大尺度环流背景、中尺度环境条件、物理量场及垂直螺旋度等方面分析2015年8月31日发生在华北地区的一次区域性暴雨天气过程，总结这次暴雨过程的形成机制，为类似形势暴雨的预报提供有利的依据。结果表明：东高西低的环境背景形势下，副热带高压的强盛使得上游系统维持，贝加尔湖暖脊的发展导致东北低涡的南落是此次暴雨的发生背景。中层冷空气的入侵及低层暖湿气流的输送促使不稳定能量释放，触发了短时强降水等强对流天气的发生发展。水汽通量大值区和其辐合中心的叠加区域与暴雨落区有着很好的对应关系。高层辐散、低层辐合的抽吸耦合作用使得上升运动加强，为此次暴雨过程提供了充足的动力条件。假相当位温可以有效判定暴雨发生时段大气的稳定度，进一步判断暴雨发生时段与落区。低层垂直螺旋度正中心大值区对强降水落区及强度的判断有着很好的指示意义。

Using the conventional weather data and the NCEP1/1 degree interval 6h reanalysis data, the synoptic di- agnosis method was adopted to analyze a regional storm weather process in North China from the large scale circula- tion background, the mesoscale environment conditions, the physical quantity field and the vertical heficity, and sum- marized the rainstorm process in August 31, 2015. The formation mechanism provided a favorable basis for the fore- cast of similar situation rainstorm. The results showed thatwith the topographical characteristics of higher east than west in North China, this rainstorm event was laid out as the strong subtropical high maintained upstream weather sys- tems and the northeast vortex moved southwards due to the development of a warm ridge at Lake Baikal. The intru- sion of mid-level cold air and moisture transport from warm humid low-level draft facilitated the release of unstable energy and triggered severe convective weather such as short-time heavy rainfall. The intersection area of the high moisture flux zone and the convergence center corresponded well with the rainstorm area. The coupling of upper-lev- el divergence and low-level convergence induced strong upward motions, providing the rainstorm with sufficient dy- namic conditions. Pseudo-equivalent potential temperature can be employed to effectively determine the atmospheric stability and the occurrence time and area of the rainstorm. The center of large low-level vertical helicity area plays an important role in determining the heavy rainfall zone and estimating the rainfall intensity.