2007年4月23日广东飑线的移动和地面中尺度结构特征分析

On the Motion and Mesoscale Surface Structure of a Squall Line on April 23, 2007 in Guangdong

基于观测和分析,研究了2007年4月23日发生在广东的一次飑线的移动预报因子和地面中尺度结构特征。结果表明,该飑线的移动与1000~500 hPa等厚度线的走向以及飑线前部的低空垂直风切变方向基本一致。同时该飑线的移动方向还可通过Corfidi矢量法,由低空急流的反向矢量和850~300 hPa层间的平均风速矢量合成得到。该飑线具有显著的地面中尺度结构特征,其中包括地面风场的辐合辐散线以及飑前中尺度低压、雷暴高压和尾流低压等。飑线前部有很强的辐合,对应强降水区有很强的辐散,后部也有明显的辐合,雷暴高压处在辐散中心附近,尾流低压则处于飑线后部辐合线之后。另外,还将该飑线的移动和地面中尺度特征与美国的飑线做了对比分析。

The movement and the mesoscale surface structure of a squall line on April 23,2007 in Guangdong is explored based on observations.It is shown that the moving direction of the squall line is parallel to the contours of the 1000–500 hPa layer thickness and the low-level vertical wind shear in front of the squall line.Meanwhile,the motion of the squall line can be estimated by the sum of inversed low-level jet and mean flow in the 850–300 hPa layer as proposed by Corfidi.Typical mesoscale surface structure of a squall line is observed including convergence and divergence lines,prelows,storm highs and wake lows.There is strong convergence line at the leading edge and in the back part of the squall line,and strong divergence line corresponding to the precipitation areas.The storm highs are between the divergence line and the convergence line in front of the squall line but much closer to the former,while the wake lows are behind the convergence line in the back of the squall line.These features of Guangdong squall line are also compared with those of squall lines in America.