热带气旋影响下2007—2021年苏皖地区龙卷活动情况及环境特征统计分析

Statistical analysis of tornado activity and environmental characteristics under the influence of tropical cyclones in Jiangsu and Anhui area from 2007 to 2021

本文收集并统计了2007—2021年热带气旋(Tropical Cyclone,TC)影响下苏皖地区的65次龙卷记录,其中TC(登陆)龙卷24次,TC(海上)龙卷41次。江苏龙卷多于安徽,呈南多北少分布,低海拔平原郊区为易发地带,7、8月的午后至傍晚为易发时段。登陆TC引发龙卷时,强度级别主要为热带低压和热带风暴,多以西北向路径在福建及浙江沿海登陆,龙卷多出现在以TC为中心300~550 km的东北象限,该区域内存在中等强度的不稳定能量、强的低层切变以及大的风暴相对螺旋度和能量螺旋度。海上TC引发龙卷时的强度级别主要以热带风暴、强热带风暴和台风为主,有3种主要移动路径:偏西路径、西北路径和偏北路径。TC(海上)龙卷发生时TC多在25°N以南,此时苏皖地区受副高和TC的共同影响,西南暖湿气流不断输送,配合中纬度的低槽活动,冷暖空气对峙,有利于龙卷生成,虽动力条件弱于TC(登陆)龙卷,但热力条件更好,能量螺旋度值较大。

This paper collected and counted 65 times of the tornado records in Jiangsu and Anhui Province under the influence of Tropical Cyclone(TC)from 2007 to 2021 including 24 TC(landing)tornadoes and 41 TC(offshore)tornadoes.There are more tornadoes in Jiangsu than in Anhui,more in the south than in the north.The suburbs of the low altitude plain are prone to occur,and the afternoon to evening in July and August are prone to occur.When landing TC causes tornado,the intensity level is mainly tropical depression and tropical storm.Most of them land in Fujian and Zhejiang coastal areas along the northwest route.Tornadoes mostly appear in the northeast quadrant of 300-550 km with TC as the center.There are medium intensity unstable energy,strong low-level shear,and large storm relative helicity and energy helicity in this area.The intensity level of tornado caused by TC at sea is mainly tropical storm,strong tropical storm and typhoon,and there are three main moving paths:the path to the west,the path to the northwest and the path to the north.When TC(offshore)tornadoes occur,TC is mostly in the south of 25°N.At this time,Jiangsu and Anhui regions are jointly affected by the subtropical high and TC,and the southwest warm and wet air flow is continuously transported.In combination with the low trough activity in the middle latitude,the cold and warm air confrontation is conducive to the formation of tornadoes.Although the dynamic conditions are weaker than TC(landing)tornadoes,the thermal conditions are better,and the energy helicity value is larger.