内蒙古巴彦淖尔市一次强降水过程诊断分析

Diagnostic Analysis of a Heavy Rainfall in Bayannur,Inner Mongolia

运用常规气象资料和自动站实测资料,从低涡系统的演变规律及物理机制等方面对2010年9月6-9日发生在内蒙古巴彦淖尔市一次强降水过程进行诊断分析。结果表明:此过程是在中高纬稳定的大尺度环流背景下,由地面气旋、低涡和副热带高压共同作用下产生的,东移的冷空气与西南暖湿气流在巴彦淖尔市上空交绥是造成此次强降水的主要原因。充足、稳定的水汽输送和较强的水汽辐合,为此次强降水提供了充足的水汽条件。高空强烈的辐散,通过抽吸作用引起低层强烈的辐合,从而促使垂直上升运动增强,是此次降水天气发生的动力。500 hPa层以上大气层结稳定,阻挡暖湿空气向上输送,促使不稳定能量在500 hPa层以下积累,为此次强降水发生提供了足够的能量条件。850 hPa偏东风暖湿气流受阴山的阻挡和抬升,降水量增加,而山后降水量减少。乌拉山与白云查汗山形成狭长山谷,边界层东风气流穿过,狭管效应有利于此地风速增大,将大量的水汽输送到巴彦淖尔市上空。

Using conventional meteorological data and automatic weather station measured data, a heavy rainfall process occurred in Bayannur, Inner Mongolia on 6 to 9 September in 2010 was analyzed diagnostically from the evolution law and physical mechanism of low vortex system. The results showed that： this process occurred in the background of stable large-scale circulation in middle and high latitudes, caused by the joint action of ground cyclone, low vortex and subtropical high. And the main reason of the heavy rainfall was the junction of the cold air moving eastward and the southwest warm wet flow. The adequate, stable water vapor transport and strong water vapor convergence provided adequate moisture conditions for the heavy rainfall. High-level strong divergence caused the strong low-level con- vergence by the pumping action, thus contributing to the enhanced vertical upward movement, and it was the driving force of the precipitation. The stable layer above 500 hPa block warm and moist air upward transportation prompted the unstable energy accumulated under 500 hPa, and provided enough energy for the heavy rainfall. The 850 hPa easterly warm and moist flow was blocked and uplifted by Yinshan, so the precipitation increased, while the precipitation decreased behind the mountain. Ural hill and Baiyunchahan hill formed a long and narrow valley, when the easterly flow passed through the boundary layer, the effect of narrow was conductive to the increase of the wind speed, and transported a large amount of water vapor to Bayannur city.