2012年6月狼山脚下罕见大暴雨天气过程分析

利用Micaps数据、数值预报产品及自动气象站资料,对2012年6月25—28日发生在狼山脚下的大暴雨过程成因进行分析。结果表明:⑴500hPa亚洲中高纬在两脊一槽型环流背景下,贝加尔湖冷涡底部东移的短波槽与副热带高压(简称副高,下同)、维持阶段中低层切变辐合系统垂直叠置激发的两次对流性强降水和副高东退阶段冷槽东移时形成的锋面降水相累加,是此次大暴雨的主要成因。⑵冷涡底部分裂东移的短波槽为触发强对流提供了动力条件。副高西伸北抬,河套东高西低形势建立,副高外围偏南和东南水汽通路形成与维持,为暴雨产生和持续提供了水汽输送条件。高、低空切变、辐合系统垂直叠置形成的动力不稳定;高、低层冷暖平流造成的热力不稳定;长时间水汽和热量输送、积聚,使高能、高湿舌伸入狼山南麓形成的位势不稳定;狼山脚下三面环山形成的地形抬升作用叠置在不稳定区上空,是强对流爆发的抬升条件。⑶副高西伸、维持、东退阶段是否相继出现并均能形成有利的强降水形势,达到强降水指标,是大暴雨预报的着眼点。

Cause Analysis on Rare Rainstorm Weather Process at the Foot of Wolf Mountain in June 2012

By using the Micaps data, Numerical （brecast products, satellite images, radar echo and data of automatic weather station, this article analyzed the causes of heavy rain process occurred at the foot of Wolf Mountain on June 25-28, 2012. The results showed that： （1） The 500hPa Asia in mid-high latitudes was in the context of two ridges and a groove circulation, at the botlom of Lake Baikal cold vortex eastward shift of the short wave trough and westerly extension of the subtropical high, the accumulation of two convective strong precipitation stimulated by the vertically stacked low level shear convergence system in the maintenance stage and the frontal precipitation formed by the eastward coht trough during the eastward withdrawal stage of the subtropical high, is the main causes of the heavy rain.（2） The split eastward shift short wave trough at the bottom of the cold vortex provided the dynamical condition; subtropical high extended west and northward, and the situation of high East and low West in Hetao, the tormation and maintenance of southerly and southeast water vapor channel in the out-ring of the subtropical high provided the water vapor transport conditions for the production and substance of storm. The dynamic instability caused by high and low altitude shear and the vertically stack of convergence system, the thermal instability caused by high and low level cold or warm adveetion, potential instability formed by prolonged moisture and heat transportation, accumulation caused the high-energy, high humidity tongue stuck at the southern foot of Wolf Mountain, and the topographic uplift formed at the foot of Wolf Mountain where was surrounded by mountains on three sides superimposed over the convergence zone, were the uplift conditions of the outbreak of the strong convective. （3） The focus of heavy rain forecast was whether it can emerge one after another and all form the favorable situation of the heavy precipitation, to achieve strong precipitation index in the stage of westerly extensi