巴彦淖尔市“8.16”局地大暴雨过程诊断分析

A Diagnostic Analysis on "8.16" Local Torrential Rain Process in Bayannur

文章利用常规气象观测资料、数值预报产品和自动站资料,对2008年8月15—18日发生在巴彦淖尔市一次局地大暴雨天气过程进行诊断分析。结果表明:(1)在降水前期,位于贝湖脊下深厚的"高压盖"将500hPa西南水汽和700hPa东南水汽拦截在河套南部,为暴雨产生聚集了水汽;(2)从孟加拉湾经四川伸向巴彦淖尔市的高能、高湿舌,为暴雨形成输送了潜在的不稳定能量;(3)西伸副高与东移的贝湖高压脊叠加建立的东高西低环流背景,为强降水在暴雨区滞留起到了阻挡作用;(4)500hPa西来小槽推开"高压盖"后产生的辐合上升区和700hPa切变线叠加后,与200hPa高空急流出口处左侧辐散槽区在巴彦淖尔市上空叠置,是形成暴雨的动力抬升条件,也是产生本次暴雨的触发机制。高、中、低层中、小尺度切变、辐散、辐合流场垂直叠置,高能、高湿、强辐合、强上升区同时具备,是本次暴雨的预报着眼点。

This article used convention meteorological observation data, the product of numerical forecasting and the data of automatic station, the weather process of torrential rain that occur on August 15-18, 2008 in Bayannur was diagnostic analyzed .The results showed ：（1）At the prior period of precipitation, the thick “high-pressure-cover” that under Baikal Lake pressure ridge headed off the 500hpa southwest vapor and the 700hpa southeast vapor in south of Hetao, and collected the vapor for torrential rain ; （2）The tongue of high-energy and high-humid from Bay of Bengal, pass by Sichuan and run out Bayannur, transported latent and instable energy for forming the torrential rain; （3）The westerly subtropical high superposed with the easterly Baikal Lake pressure ridge ,and formed the background of circulation that was high east and low west, and had an effect on holding up the retention of heavy precipitation in the area of torrential, rain;（4）The area of convergence ascending area which formed fromi 500hpa westerly trough daffed the “high-pressure-cover” and converged with 700hpa Shear line, subsequently, it converged with 700hpa divergence trough that located in the left of upper-level jet stream export in the air of Bayarmur city, this is the Condition of lifting and trigger mechanism for torrentical rain. The vertical superposition of micrnscale-shear, divergence and convergence flow field in the upper-level, middle-level and low-level on medium and small dimensions, also the mesescale-shear and high-energy, high- humid, convergence, the area of lifting was the key of forecasting.this torrential rain.