ANALYSIS OF EF2~EF3 TORNADO ON JULY 22, 2020 IN NORTHERN JIANGSU PROVINCE
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摘要: 利用常规观测、地面自动站及江苏宿迁、淮安、盐城多部多普勒天气雷达对2020年7月22日发生在江苏北部EF2~EF3级龙卷天气过程进行了详细分析。(1)此次龙卷过程有利的环境场包括低层0~1 km强垂直风切变,中低层充足的水汽、较低的抬升凝结高度以及较强的辐合上升运动。前期持续性降水、中层冷空气入侵,层结不稳定度加强,为龙卷的发生提供了潮湿不稳定环境。(2)龙卷对流风暴在地面辐合线附近形成并发展增强,在龙卷发生地附近有局地小尺度涡旋形成,伴随有地面辐合中心沿着地面辐合线向偏东方向移动。龙卷发生前后,地面自动站出现风速突增,风向突变、气压下降并伴有短时强降水。(3)导致此次龙卷的超级单体生命史长达3小时,在其东移过程中伴有深厚的中气旋和TVS特征,首次识别出中气旋是位于风暴中层,约2.6 km高度,之后逐渐在垂直方向上拉伸发展;而TVS底高维持在1 km左右,强度维持在60×10-3 s-1左右。当中气旋底高较低且切变值持续较强时,结合地面中尺度系统演变为龙卷有效临近预警提供了可能。Abstract: Based on the data from conventional observation, ground intensive observation, and the Doppler weather radars in Suqian, Huai' an and Yancheng, Jiangsu Province, the present study analyzed the tornado that happened on July 22, 2020 in northern Jiangsu Province. The research shows that: (1) The favorable environmental fields of this tornado included a strong 0~1 km vertical wind shear in the lower layer, sufficient water vapor in the middle and lower layers, low uplift condensation height, and strong convergence and upward movement. At the early stage, the continuous precipitation and cold air intrusion in the middle layer strengthened the stratification instability, providing a humid and unstable environment for the tornado. (2) The convective storm that caused the tornado originated near the surface convergence line. There were small-scale local vortices in the vicinity of the tornado and the ground convergence center moved eastward along the ground convergence line. Before and after the tornado, the surface wind speed near the surface vortex suddenly increased, the wind direction suddenly changed, the air pressure significantly decreased, and there was short-term heavy precipitation. (3) The supercell that caused the tornado had a life history of 3 hours. During its eastward movement, it was accompanied by deep mesocyclone and showed tornadic vortex signature (TVS). The first mesocyclone was detected in the middle of the storm, about 2.6 km in height, and then it gradually stretched vertically. The TVS bottom height was maintained at about 1km, and the intensity was maintained at about 60 ×10-3 s-1. When the base height of the mesocyclone is low and the shear value continues to be strong, combined with the evolution of the ground mesoscale system, it is possible to provide effective early warning of tornadoes.
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Key words:
- northern Jiangsu Province /
- tornado /
- supercell /
- mesocyclone
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表 1 7月22日淮安、盐城中气旋特征
地点 时间 ID 底高/顶高(km) 径向/切向直径(km) 最强切变/高度(10-3s-1/km) 20:22 J0 1.5/3.2 4.2/7.5 7/3.2 20:39 J0 1.5/3.1 13.2/8.3 33/1.5 20:56 D0 1.2/2.7 3/5 9/1.2 21:08 N0 1.4/4.4 3.8/2.9 36/4.4 21:14 N0 1.3/7.8 2.5/3.8 37/1.3 21:20 N0 1.4/6.2 3.5/2.1 37/1.4 21:25 N0 1.4/6.6 6/8.3 31/1.4 21:37 D0 1.5/5 3.5/3.1 31/5 淮安 21:43 D0 1.5/7.8 4.2/2 38/7.8 21:49 D0 4.6/7.4 14/10.4 36/6 21:54 D0 1.5/6.4 7.5/6.4 17/1.5 22:06 D0 3/7.6 6.5/3.4 33/3 22:12 D0 3.1/6.7 4.2/3.1 31/3.1 22:18 D0 4.9/6.7 3.8/3.1 31/4.9 22:23 N6 3.2/6.8 2.5/2.6 30/3.2 22:29 N6 3.4/7 4/5.5 28/3.4 22:41 N6 3.8/5.8 4.2/2.9 27/5.8 21:30 A1 6.1/7.1 5.8/4.1 24/7.7 21:47 A1 2.0/4.0 7.8/11.4 22/2 21:58 A1 3.5/5.2 9.5/10.6 18/5.2 22:04 J0 1.6/6.9 10/11.6 30/5 22:10 H0 1.6/6.7 4.2/7.1 27/6.7 22:15 H0 1.5/7.8 2.2/3.8 34/7.8 盐城 22:21 N0 2.9/7.3 15.2/4 38/7.3 22:27 N0 1.4/7.9 4.5/2.2 37/7.4 22:33 N0 1.4/6.9 7.2/3.8 39/6.9 22:38 N0 1.2/7.1 6.8/4.5 9/1.2 22:44 N0 1.2/5.4 3.2/6.4 11/1.2 22:50 G9 1.2/4.1 7.8/5.5 12/1.2 22:56 N0 1.2/5.0 6.8/5.8 35/1.2 表 2 7月22日淮安、盐城TVS特征
地点 时间 ID 底高/顶高(km) 特征深度(km) 最低仰角速度差(m/s) 最强切变/高度(10-3s-1/km) 淮安 20:22 J0 1.4/4.6 4.6 18 21/1.4 20:39 J0 1.5/6.2 6.2 53 65/1.5 20:45 J0 1.5/6.5 6.5 53 63/3.2 20:51 J0 1.4/3.1 3.1 51 68/1.4 20:56 N0 1.5/3.3 3.3 17 63/3.3 21:08 N0 1.5/7.7 7.7 53 65/1.5 21:14 N0 1.5/7.9 7.9 28 64/1.5 21:20 D0 1.3/5.8 5.8 51 67/1.3 21:25 N0 1.3/7.6 7.6 50 66/1.3 21:31 D0 1.4/7.4 7.4 25 67/2.9 21:37 D0 1.4/7.6 7.6 33 67/4.5 21:43 D0 1.5/7.7 7.7 23 68/7.7 22:15 H0 1.5/7.9 6.4 35 60/7.9 22:27 N0 1.3/7.5 6.2 38 69/7.5 22:33 N0 1.2/7.1 5.9 50 70/7.1 盐城 22:38 N0 1.2/7 5.8 31 40/1.2 22:44 N0 1.2/6.9 5.6 53 68/1.2 22:50 B0 1.1/6.8 5.7 32 44/1.1 22:56 N0 1.1/6.8 5.6 29 39/1.1 -
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