2014年巴彦淖尔市一次强降水天气成因分析

Cause Analysis on Heavy Precipitation Weather in Spring of 2014

文章利用常规气象观测资料,针对巴彦淖尔市2014年5月23日的一次强降水天气过程,分别从形势场、物理量场、单站资料等方面进行了诊断分析。结果表明：（1）高空500hPa中高纬度天气形势发展为东脊西槽的经向型环流,上游西南引导气流的建立为暖湿气流向北输送提供了条件。700-850hPa在我市上游形成的冷涡系统并逐步演变为＂人字形＂切变对强降水的产生起到了决定性作用,同时配合T-Td≤5℃的湿区、上游弱冷平流的进入及下游暖高脊稳定少动,为强降水的产生提供了较好的水汽条件。（2）强降水主要产生于＂河套气旋＂形成的冷锋前暖锋后,低压带南北向且狭长,为低层辐合高层辐散提供了基础条件。（3）随着上升垂直运动的逐渐加强,散度、涡度相互配合,低层辐合高层辐散作用明显,对强降水的发生提供了动力条件。（4）从河套南部伸向蒙古地区的高能舌,致使河套地区形成了深厚的暖湿气层,这个暖湿气层的存在为强降水储存了潜在的不稳定能量。（5）单站K≥34℃易产生强对流及强降水等天气。

By using conventional meteorological observation data, a diagnostic analysis was made respectively from aspects of the weather system, physical quantity field, single station information, etc. The results showed that：（1） the weather situation at 500 hPa at mid high latitude developed into meridional circulation with east ridge and west groove, and the establishment of southwest steering flow in the upstream region provided the condition for northward transportation of warm moisture air. 700-850 hPa cold vortex system formed in upstream of the city gradually evolved into ＂herringbone＂ shear played a decisive role in producing heavy rain, in conjunc-tion with wet area T-Td≤5 ℃, the entry of weak cold advection in the upstream and the high ridge in the downstream remaining stable provided better water vapor condition and weather condition to the heavy rain.（2） the heavy rain occurred mainly before the cold front and behind the warm front formed from ＂Hetao cyclone＂, low pressure belt was long and narrow in an North-South direction provided basic conditions for the low-level convergence and high-level divergence.（3） With the gradual strengthening of the vertical emergence, interaction of divergence and vorticity, the low-level convergence and high-level divergence affected obviously offered dynamic condition to the heavy rain.（4）the high energy tongue extended from southern Hetao to Mongolia resulting in deep warm and moist air layer. Existence of this air layer stored potential instable energy of heavy rain.（5） The K index of single station more than34℃ becomes more prone to severe convection and heavy precipitation and other weather.