2007年夏季河套地区两次区域性大暴雨过程模拟分析  

Simulation and Analysis of Two Regional Summer Heavy Storm of 2007 in the Great Bend of the Yellow River

作　　者：周丽峰[1] 李韬 

机构地区：[1]陕西省气象台,西安7100142 [2]陕西省气象遥感中心,西安710014

出　　处：《科技导报》2008年第24期43-50,共8页Science & Technology Review

摘　　要：以2007年夏季发生在河套地区的两次大暴雨天气过程为对象,利用MM5中尺度数值预报模式对其发生发展过程进行数值模拟,通过与实况对比,表明模式对暴雨落区的模拟是成功,然后利用模式输出结果对暴雨形成机制在影响天气系统、水汽输送、不稳定层结和动力条件等方面进行了诊断分析。结果表明,两次大暴雨都发生中高纬十分稳定的环流形势下,在第一次暴雨过程中,西北涡和低空西南急流是其主要影响系统,低涡东侧的辐合和低层暖湿气流为暴雨的发生提供了良好的动力和水汽条件;在第二次暴雨过程中,500hPa切变线为其主要影响系统,高层强烈的抽吸作用为暴雨区提供了强劲的上升运动,弱冷空气与低层暖湿气流之间形成强烈位势不稳定为暴雨的发生发展提供有利的条件。第一次暴雨过程中一直有高通量水汽输入,水汽由来自孟加拉湾和南海的两股偏南气流合并而成;第二次暴雨过程的水汽有台风"帕布"东北侧的偏东气流输送。与第一次暴雨过程无冷空气作用不同,第二次暴雨过程中由于有弱冷空气侵入触发了不稳定能量释放,更有利于暴雨的产生和形成。低层螺旋度正值区与未来12～18h暴雨落区有较好的对应关系,暴雨区高层为螺旋度负值区,螺旋度这种高低层耦合是触发和维持暴雨的动力机制。The paper presents a numerical simulation of the two regional summer heavy storms of 2007 in the great bend of the Yellow River by MM5, as shown to be a successful simulation by a comparison between the simulation and the real scene. A diagnostic analysis is made on weather system, transfer of water vapor, unstable stratification and dynamic conditions of the storm＇s generative mechanism. It was showed that the two heavy storms were generated in a stable circumfluence in the middle and high latitudes. The northwest vorticity and southwest jet stream in the low level are the main weather systems of the first storm with convergence in the east of vorticity, with warm and humid air in the low level providing favorable dynamic and vapor conditions for the storm. The shear line at 500 hPa is the main effective system of the second storm, with strong pumping action in higher level promoting a powerful uplift in the storm area, at the same time, the obvious potential energy between weak cold air and warm and humid stream is conductive to the generation and development of the storm. In the course of the first storm, there is a high flux water vapor transporting all the time, which is the merging of the pre-south air-flow from Bay of Bengal and South China Sea, while the water vapor in the second storm is from the pre-east air-flow in the northeast of typhoon Sepat. There is a difference between the two storms that the second storm＇s generation results from the unstable energy from weak cold air＇s invasion, which is more effective for the birth and forming of storm. Helicity positive area in lower lew：l has a good corresponding relationship with the storm area in the coming 12-18 h, the higher level in the storm area shows the helicity negative area, which is the dynamic mechanism for triggering and preserving storms.

关 键 词：河套地区 暴雨 数值模拟 影响系统 螺旋度 

分 类 号：P458.121.1[天文地球—大气科学及气象学]