2006年6月皖北龙卷多普勒雷达产品分析

Analysis of a Tornado in Northern Anhui in June 2006 Based on Doppler Radar Products

分析了2006年6月29日发生在安徽泗县的龙卷多普勒雷达的中气旋和龙卷涡旋特征(TVS)等产品。龙卷发生前,卫星云图上有3个对流云团呈东北—西南向排列,每个云团的东南侧有弓状回波发展,3条弓状回波首尾相连,也呈东北-西南向排列,龙卷发生在最西南的弓状回波的顶部。龙卷发生前弓状回波在上游产生了短时强降水,2 h降水量达到60 mm以上。在弓状回波的前沿,雷达探测到一系列的中气旋,龙卷发生前30 min,最西南的弓状回波追上其前面的回波带,发生了2个回波带合并,回波合并前,回波带上有2个中气旋,回波合并后,探测到一个特大直径的中气旋(径向直径25.8 km)。在龙卷发生地的上游,有一条带状的灾害性大风区,实地位置测定结果,该带状大风区与一系列中气旋最大风速圈的南边缘移过的路径一致。分析认为中气旋最大风速圈的南边缘,中气旋的风向与弓状回波后的直线风方向相同,两者叠加造成灾害性大风。出现龙卷1 h 40 min之前(05:00),在泗县上游淮北地区,雷达开始探测到中气旋产品,在12 min之前探测到TVS(龙卷涡旋特征)产品,这些雷达产品对大风灾害的临近预报无疑是非常有用的。

The Doppler Radar Products during a tornado occurred in Sixian,Anhui Province on 29 Jun 2006 are analyzed.Before the tornado,there were three NE-SW oriented bow-shaped echoes,and the tornado was on the furthest southwest edge of the bow-shaped echo.A short-range heavy rain occurred before the tornado appearing with a rainfall amount of 60 mm in 2 hours.The strong shear of wind direction existed in the front of the bow-shaped echo,which resulted in a series of mesocyclones along the front edge of the echo.The southwest bow-shaped echo joined the echo in the front of it,30 min before tornado occurred,and then a large mesocyclone with a diameter of 25.8 km formed.According to the survey,there was a severe wind zone in upstream of the tornado,which was in agreement with the moving path of the south edges of the maximum zones in the mesocyclones.It suggests that along the south edges of the maximum wind zones in the mesocyclones,the mesocyclones and the straight wind behind the bow-shaped echoes have the same direction,and the two airflows overlaid together,leading to the occurrence of the severe winds.About 1 hour 40 min before tornado occurred,the radar caught up the mesocyclones,and 12 min before,detected TVS（Tornadic Vortex Signature） products,which are undoubtedly useful for making tornado warning.