1804号台风“艾云尼”龙卷分析

An analysis on tornadoes in typhoon Ewiniar

  • 摘要: 2018年6月8日,在1804号台风“艾云尼”螺旋雨带中发生了两次陆龙卷天气,分别袭击了广州市南沙区横沥镇和佛山市南海区大沥镇。利用广州CINRAD/SA多普勒天气雷达、佛山CINRAD/XD多普勒天气雷达、5 min间隔的地面自动气象站和MICAPS等资料,研究了两次陆龙卷的天气背景、环境参数和龙卷风暴中尺度结构特征。结果表明:广州南沙龙卷为台风环流外围龙卷,位于台风中心的东北象限,强度为EF3级;佛山南海龙卷为台风环流内部龙卷,位于台风中心的东侧,强度为EF1级。龙卷均发生在中低空强东南急流在珠江口附近上下叠加和高层辐散的有利大尺度环流背景下。环境条件表现为较强的低层风垂直切变和较大的风暴相对螺旋度(SRH)、较小的对流有效位能(CAPE)和对流抑制能量(CIN)、极低的抬升凝结高度(LCL);地面存在中尺度辐合线和小尺度涡旋。广州S波段雷达探测到两次龙卷母风暴的低层钩状回波和入流缺口回波特征及低层中等强度中气旋,龙卷出现在钩状回波顶端、中气旋中心附近。佛山X波段双偏振雷达清晰地探测到佛山南海区大沥龙卷的微型超级单体和龙卷碎片特征(TDS)。

     

    Abstract: Two tornadoes occurred in the spiral rain-band of typhoon Ewiniar (1804) on 8 June 2018. They struck Hengli town of Nansha district in Guangzhou city and Dali town of Nanhai district in Foshan city, respectively. Using various observation data, the synoptic environment and radar echoes for the tornadogenesis were analyzed. The results show that the tornado at Guangzhou was rated EF3 and located at the peripheral of typhoon Ewiniar in the northeast quadrant, while the tornado at Foshan was rated EF1 and developed in the inner region of Ewiniar to the east of its center. The synoptic environment for the above tornadoes show a typical circulation pattern with upper-level divergence, coupled with strong southeasterly jets at mid- and low-level over the Pearl River Estuary. The environmental conditions for the tornadogenesis include strong low-level vertical wind shear, high storm relative helicity, weak CAPE and CIN and low LCL. There were mesoscale convergence lines and small-scale vortices in the surface. Hook echoes, Fin echoes and moderate mesocyclones of tornado storms in low-level can be detected in observations of the CINRAD/SA radar. The tornadoes were located at the top of the hook echoes and near the center of mesocyclone. The features of mini supercell and tornadic debris signatures (TDS) were more obvious at Foshan CINRAD/XD radar observations than in observations of Guangzhou CINRAD/SA radar, which is deployed in Dali town of Nanhai district.

     

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