2007年7月皖苏北部龙卷风初步分析

Analysis of Tornado Events in North Anhui and Jiangsu Provinces in July 2007

2007年7月3日0840—1000(UTC)先后在安徽天长—江苏高邮和江苏兴化等局部地区发生了多个龙卷风,成为本年度的极端天气事件之一。利用高频次的FY-2C、2D等静止气象卫星资料、南京站多普勒天气雷达资料和常规天气资料对这次龙卷风天气系统的活动与演变进行了分析,得到以下认识:叠加在梅雨锋切变线上的高空短波槽线,及槽后强干冷空气平流与低空暖湿平流在垂直方向迭合,并与200hPa青藏高压东西向脊线北侧的辐散场重合,为强对流天气系统的发展提供了动力和热力条件;0400(UTC)之后,在鄂豫皖苏交界区形成了两条中尺度对流云带。一条是与梅雨锋切变线相对应的弱对流云带,另一条是位于其南面的在上述干冷空气前沿迅速发展的飑线云带。切变线弱对流云带整体缓慢向南移动,构成云带的对流云块沿着云带缓慢向东移动。强对流飑线云带则由西北西向东南东方向移动,构成飑线云带的强对流云团则沿着云带由西南西向东北东方向移动。龙卷风就发生在上述两条中尺度对流云带的云团相交合并处。

There were many tornadoes produced in the area between Tianchang of Anhui Province and Gaoyou of Jiangsu Province, and also in Xinghua of Jiangsu Province between 0840 - 1000UTC on July 3,2007, It was one of the extreme weather events of 2007, High temporal resolution geostationary satellite of FY-2C and 2D, Nanjing Doppler weather radar data and routine meteorological data were used in analyzing the evolution of the weather system. The main conclusion was as follows： The dynamic and thermal conditions for strong convection development were provided by the combination of the short wave trough with cold dry air at high altitude, warm moist air advection at low altitude and the divergence field at the north of the ridge line of Tibet high pressure. After 0400UTC, two mesoscale convective cloud belts were developed in the co-boundary area of Anhui, Henan, Huhei and Jiangsu provinces. One of them, corresponds to the shear line on Meiyu front and is rather weak. The other was the fast developing squall line at the south of the first cloud belts and in front of the cold air mass. The weak convective cloud belt moved south slowly. The convective cells in it propagated toward east. The squall line moved from west northwest to east southeast. The strong convective cells in it propagated from west southwest to east northeast. The tornadoes developed in the area where the convective cells in two mesoscale convective cloud belts merged.