一次致雹强风暴的多普勒雷达特征分析

利用NCEP再分析资料和北京、天津的多普勒天气雷达产品对2007年7月9日华北中部地区一次伴有短时暴雨、局地冰雹和短时大风等强对流天气过程进行分析研究。分析表明,此次天气过程发生前高空转为前倾槽,并具有较强的不稳定层结;近地层的风切变线是雷暴生成的条件。物理量诊断分析表明：降水前水汽辐合区已从近地层扩展到850 hPa,但比较浅薄;低层辐合、高层辐散的配置加强了垂直上升运动;强对流天气发生区域处于垂直上升运动最强的区域内。多普勒天气雷达产品分析表明：致雹风暴具有中气旋特征和类似强降水超级单体的性质;路径预报的准确率与雷暴的总数目和移动异向性有关,雷暴的实际移向角度与雷达的路径预报相比存在明显偏差,总体偏差在29～67°之间,但路径预报产品仍对天气预报具有一定指示性;风廓线产品中3-7 km高度内垂直风切变矢量随高度呈顺时针旋转,在这种有利的条件下风暴有可能发展成强降水超级单体。

Characteristic Analysis of Doppler Radar About a Hailstone Severe Storm

We studied a local convective weather occurred in the central north region on 9 July 2007, during which short-time rainstorm, local hailstone and short-time heavy wind were all happed, with the NCEP reanalysis data and Doppler weather radar products of Beijing and Tianjin. Analysis showed the tilted trough became forward from backward, and stratification became more judder on bottom layer, in this context the shear line of wind near ground was the condition of the storm growing. Some a- nalysis of physical quantity showed information including： the moisture convergence had spread from ground to 850 hPa before rain but it was shallower; convergence of lower layer and divergence of higher layer strengthened vertical motion; the storm occurred in the area of the strongest vertical motion. Based on the Doppler weather radar products, we distinguished that the storm had characteristic of mesocyclone and similar heavy precipitation supercell; the accuracy rating about storm tracking information was related to numbers and different movements of all storms; there were some deviations between actual direction of storm and the forecasting route of radar, its total variation was between 29--67 °, but the storm tracking information still had certainly indicative helpfulness on short-range prediction; the wind-profiling product emerged perpendicular wind shear spin round on clock-wise between 3--7 km high level, on this helpful condition the storm maybe developed and became heavy precipitation supercell.