2008年初江苏暴雪天气的模拟分析

Simulation analysis of snowstorm weather in early 2008

利用常规探测资料,分析2008年1月27—28日淮河以南的区域性暴雪天气过程发现:暴雪发生在巴尔喀什湖阻塞高压东侧不断补充南下的冷空气与低空的西南急流输送的暖湿空气相结合的背景条件下,中低层的气旋式环流及其东侧的暖式切变线是暴雪天气的主要影响系统。PSU/NCAR非静力原始方程中尺度模式MM5V3.6较好地模拟了暴雪过程。高分辨率的数值模拟资料显示:水汽通量散度和垂直运动的特征揭示了700 hPa以上的中层的大气运动是暴雪发生的关键;整层的气温均在0℃以下,为降雪提供了充分的气温条件。通过对位涡、湿位涡的诊断发现,冷空气由中层自北向南向低层楔入,导致暖湿气流加强了的垂直运动沿冷空气垫倾斜上升产生对称不稳定,中尺度的对称不稳定是这次暴雪天气的物理机制。

Based on the observation data , the analysis of the regional snowstorm event occurred in south of Huaihe river during 27--28 January 2008 was made. The results showed that the background conditions of snowstorm is the combination of cold air supplemented continuously on the east side of blocking high located at Balchas Lake with low level southwest jet stream transportation of warm, moist air at the low level. The main influence systems are cyclonic circulation and shear line . Through analyzing numerical simulation data, the results showed： moisture flux divergence and vertical motion revealed that the middle atmosphere above 700 hPa is the key; atmospheric temperature of the whole atmosphere below 0 ℃ is the sufficient conditions. Through diagnostic analysis of ζp and ζm the results showed ： cold air wedging from north to south in the lower layer caused that warm and wet flow inclined upward to this cold cushion. Slantwise updraft caused symmetric instability which developed vertical motion. Mesoscale symmetric instability is the physical mechanisms of heavy snow.