一次远距离台风暴雨过程分析

Analysis of One Far Distance Typhoon and Heavy Rain Process

应用常规观测资料、卫星、雷达产品,综合分析2008年山东最强的一次降水过程,研究西风带降水系统影响山东时,远距离台风对降水的增幅作用,并对主要降水时段进行中尺度数值模拟。结果表明:在西风带系统影响山东时,远在我国东南沿海的台风右侧的东南气流产生的风向、风速辐合与西风带辐合区合并,东南风所及范围比湿增大,水汽通量辐合使大气中的垂直液态水含量明显增大。西风带系统在垂直方向上后倾,使得低层影响系统受高空槽前的正涡度平流影响,是降水发生的环流背景。中尺度模拟结果显示:前期鲁西暴雨垂直方向对流基本稳定,但有强的对称不稳定支持上升运动发展,后期半岛地区的连续暴雨则是低层增温、增湿且对流和对称不稳定并存,从而产生强降水。

By using routine observational data,satellites products,Doppler radar products, the heaviest rainfall process of Shandong in 2008 is analyzed. The role of far distance typhoon in the increase of heavy rain when a westerly rainfall system affects Shandong is discussed. The main precipitation period is simulated with MM5. The results suggest that wind direction and speed convergence zone of southeast air flow on the right side of typhoon Kalmaegi combines with westerly convergence zone. Water vapor flux convergence makes vertical liquid water content increase significantly, and the specific humidity raised in the area southeast flow reached. A backward-tilting trough in westerly causes positive vorticity advection ahead of upper trough affecting the low-impact system. Mesoscale meteorological modeling shows that the vertical convection is stable and the strong symmetry instability makes ascending motion develop in the western region of Shandong in earlier stage. Increasing temperature and humidity in low level, symmetry instability and convective instability exist simultaneously and lead to the sustained torrential rain in Shandong Peninsula in later stage.