天山北坡中部一次罕见局地强降水中小尺度系统分析

Analysis of meso-micro scale system characteristics in a rare heavy rain on the northern slope of Tianshan Mountain

利用Doppler雷达产品,结合高时空分辨率T639再分析资料,对2010年6月22日发生在天山北坡中部,石河子南部山区罕见局地强降水的中小尺度系统特征和强降水发生时间与落区进行分析。结果表明:西伯利亚至巴尔喀什湖的冷低压东南象限分裂出的中尺度短波,是造成"2010622"罕见局地强降水的直接影响系统。近低层至地面的中尺度切变线、辐合线与冷锋是局地强降水发生的触发机制。近低层存在着强盛的西南与东南暖湿气流的输送及其在天山山前的强烈辐合,为南部山区强降水的发生提供了有效水汽和不稳定能量条件。多个中-γ对流单体沿特殊地形滚动更叠是局地强降水天气落区形成的直接原因。中气旋的出现对局地强降水发生有较好的先兆性和指示意义。强降水区发生在回波强度大于50 dBz、回波顶高度大于5 km和垂直累积液态水含量大于45 kg.m-2以及中气旋的重合区域内。可由中气旋提前20 min预警短时局地强降水的发生。

Abstract：Based on the Doppler radar products and T639 reanalysis data, small-scale system characteristics of a rare heavy rain on June 22,2010 in the south of Shihezi and its occurrence time as well as falling area were ana- lyzed. The results show that mesoscale short wave split from cold low-pressure from Siberia to Lake Balkhash is the direct influencing system of this process. The middle scale shear line from low level to ground and convergence line as well as cold front are the trigger mechanism for the local heavy rain. There is the transportation of strong southwest and southeast warm-wet air flow and their strong convergence in front of the mountain near low level, which provides the effective moisture and unstable energy for this process. Multiple-γ convective cells roll and change along the special topography, which are the direct reasons forming failing areas of the local strong rain. The occurrence of meso-cyclone is indicative to the heavy rain. The heavy precipitation occurs in the superposition are- as where the echo intensity is more than 50 dBz, the echo top height exceeds 5 km, vertical accumulated liquid wa- ter content is above 45 kg·m^-2 and it exists in the mesocyclone. It is in advance about 20 rain for warning of short- time strong precipitation using mesocyclone.