山东一次台风龙卷过程灾调及环境和天气雷达特征分析

DAMAGE SURVEY, RADAR AND ENVIRONMENT ANALYSES OF A TYPHOON-INDUCED TORNADO IN SHANDONG

关键词:  龙卷  中气旋  TVS  风速评估  EF级

Key words:  tornado  mesocyclone  TVS  wind speed assessment  EF scale

摘要:

2018年8月19日受台风“温比亚”影响，山东省临沂市遭受龙卷袭击。通过实地灾情调查，给出了该龙卷的影响范围、灾害分布和强度评估等，综合考虑不同标识物和致灾过程，评估本次龙卷强度为EF3级。分析龙卷发生的环境和天气雷达特征，结果表明：龙卷发生在低抬升凝结高度（≤300 m）、强低层垂直风切变（≥18×10-3 s-1）、强相对风暴螺旋度（≥350 m2/s2）和较低对流有效位能（≤400 J/kg）的有利环境条件下；龙卷超级单体嵌于台风右侧螺旋雨带内，龙卷发生在中气旋与风暴后侧下沉气流区相接一侧，与龙卷涡旋特征位置对应；龙卷及地时中气旋向下延伸加强，同时风暴顶及单体质心迅速下降；若探测到低层中等强度中气旋时应发布龙卷预警，则此次过程的龙卷预警时间提前量为15～20 min。

Abstract:

Affected by Typhoon Rumbia, Linyi was hit by a tornado on August 19, 2018. The damage swath and distribution, and intensity of the tornado are determined based on damage survey, and the tornado intensity is rated as EF3. Based on radar and environment analyses, following results are drawn. The tornado developed in a favorable environment where the low lifting condensation level was lower than 300 m, low-level vertical wind shear was above 18×10-3 s-1, storm relative helicity was above 350 m2/s2, and convective available potential energy was less than 400 J/kg. The tornado supercell was embedded in the spiral rainband on the right side of the typhoon. As the tornado appeared on the side where the mesocyclone was connected with the downdraft area on the back side of the storm, its position corresponded to the position of the tornadic vortex signature (TVS). The mesocyclone extended downward and strengthened when the tornado touched the ground; meanwhile, the top of the storm and the center of mass dropped rapidly. If tornado warning could be issued once the low-level medium-strength mesocyclone was detected, the warning lead time of this tornado would be about 15~20 minutes.