登陆台风“摩羯”(1814)在山东引发龙卷的灾情调查与天气雷达识别

Disaster investigation and weather radar identification of tornadoes in Shandong caused by landfalling Typhoon YAGI(2018)

2018年8月13—14日,1814号台风“摩羯”(YAGI)由强热带风暴逐渐减弱成热带低压,在山东省境内造成强降水,并引发了系列龙卷。龙卷发生后,气象部门对龙卷进行了详细的实地灾情调查。通过对6处龙卷路径无人机航拍的高分辨率图像和现场勘察的建筑物损毁、树木折断、庄稼倒伏等状况的综合分析,判断发生在滨州市姜楼镇、东营市盐窝镇的龙卷达到EF2级,其他为EF0/EF1级。上述龙卷都发生在残余低压环流中心移动方向的右前方,且集中在残余低压环流外围偏北段雨带中的小型超级单体内;其中在滨州引发的龙卷距离残余低压环流中心最近,约150 km,在潍坊引发的龙卷距离残余低压环流中心最远,约400 km。这些小型超级单体在雨带中,自南向北或者自东南向西北方向移动,尺度都很小,发展高度较低,强反射率因子核位于风暴的底部,低层反射率因子的南端有入流缺口,呈钩状回波特征;低层径向速度产品有较强的正负速度对。用雷达系统原适配参数值计算表明,在调查的6次龙卷中,仅有1次龙卷发生前算出了中气旋(M)产品,2次算出龙卷涡旋特征(TVS)产品;用修改的适配参数值进行计算,在6次龙卷发生前都算出了M产品,4次算出TVS产品,优化适配参数可提前将弱的M和TVS识别出来,对龙卷的临近预警具有指导作用。

Typhoon YAGI(2018)weakened from severe tropical storm to tropical depression from 13 to 14 August 2018,which caused heavy precipitation in Shandong and induced tornados.Meteorological departments have conducted particular field investigation of tornado disasters.Based on high-resolution images of 6 tornado tracks by drone aerial photography and field investigation on damaged buildings,broken trees,and lodging crops,it is concluded that the tornados reached EF2 scale in Jianglou Town,Binzhou City and Yanwo Town,Dongying City and EF0/EF1 scale in other places.These tornados occurred in the mini supercells embedded in the outer rain bands located in the right-front direction relative to the track of residual low-pressure circulation;the tornado in Binzhou was the closest to the center of residual low-pressure circulation,about 150 km,while that in Weifang was the farthest,about 400 km.The mini supercells moved within rain bands from south to north or from southeast to northwest characterized by smaller scale,lower echo top,strong reflectivity factor at the bottom of the storm,and inflow notch and hook echo at low level;radial velocity products had strong positive and negative velocity pairs.When the original adaptation parameters of the radar system are used to calculate the mesocyclone(M)and the tornado vortex signature(TVS)products,among the 6 tornados,M can be identified for one tornado,and TVS for two tornadoes;when using modified adaptation parameters,the radar system gave out 6 Ms and 4 TVSs before the occurrence of the tornados.The weak M and TVS can be identified in advance by optimizing the adaptation parameters,which is beneficial to the warning of tornado.