摘要
利用常规观测资料、自动气象站资料及湖南省岳阳多普勒天气雷达资料对2017年8月13日东洞庭湖水龙卷(简称扁山水龙卷)进行分析。结果表明:高空辐散、中低空低压切变、边界层气旋式辐合与特殊环境共同形成强烈辐合上升流场,3个相继北上的γ中尺度低涡中第2个低涡在上升流场和前后低涡共同作用下,在扁山水域迅速加强形成水龙卷,扁山湖心自动气象站风向风速、气压、能见度等变化较为显著,但仅伴随0.2 mm阵性降水。雷达产品显示:扁山水域强辐合带北部强降水质心低、强风切变低、切变上空水平径向风速小,但整条辐合带无风暴跟踪信息、中气旋和龙卷式涡旋特征;风廓线显示扁山水龙卷形成时边界层0.6 km中气旋与0.3 km近地面辐合流场上下叠加。通过与安徽升金湖水龙卷以及洞庭湖区历史上多次龙卷进行比较,认为低空强烈气旋式辐合流场对水龙卷生消有重要作用,高空大范围辐散与中低空、边界层、地面辐合垂直叠加产生的强烈抬升抽吸作用则是扁山水龙卷的主要成因。
Based on conventional weather data,automatic weather station data,and the observation of Yueyang Doppler radar,a waterspout occurred in Bianshan waters of East Dongting Lake(Bianshan waterspout for short)on 13 August 2017 is analyzed.Results show that the cold and warm airflows converge in the East Dongting Lake area when the upper East Asian trough forces the cold air southward,and the subtropical high guides the southwestern warm moist flow northward.The quasi stationary front over the north central Hunan Province is northeast to southwest,forming an"S"curve,which is favorable for the convergence of frontal instability energy to the East Dongting Lake area.The special geographical environment is easy to trigger canyon effect,which often leads to increased wind speed and humidity.The strong divergence in front of the upper trough,the deep low-pressure shear from northeast to southwest in the middle and lower layers,strong cyclonic convergence in the boundary layer,and the special topography jointly form a strong convergent upwelling flow field.When three meso-gamma-scale low eddies on the ground move northward to Bianshan waters,influenced by combined effects of the above flow field and the front and back vortices,the second vortex strengthens rapidly and forms a waterspout.The meteorological factors such as wind speed,wind direction,air pressure and visibility recorded by the lighthouse automatic meteorological station in the lake center change significantly when the waterspout passes,while precipitation is only 0.2 mm.Yueyang Doppler radar shows that the centroid of heavy precipitation is low to the north of strong convergence zone,where shear of strong wind is moderate and the radial wind speed over the shear is low.Yueyang Doppler radar wind profiles show that mesocyclone at the height of 0.6 km and the convergent flow fields near the ground at the height of 0.3 km are superimposed when the waterspout formed at 0905 BT.Waterspouts in the southern convergence zone have no storm tracking information,mesocyclones or tornado-type vortices.However,heavy precipitation accompanied by strong subsidence and convergence at the middle and low altitudes often produce both rising and subsidence currents,which are obviously unfavorable for the formation and development of waterspouts that need huge upward pumping.Comparing and analyzing waterspout processes of the Shengjin Lake in Anhui Province and the Dongting Lake in Hunan Province,it is concluded that the funnel-shaped strong lift suction caused by large-scale divergence at high altitude and the deep low-pressure shear from northeast to southwest in the middle and lower layers,and the intense convergence of cyclones and surface cyclones in the boundary layer are the main causes of the waterspout formation.
作者
杨伟
方阳
蒋帅
袁泉
林南
Yang Wei;Fang Yang;Jiang Shuai;Yuan Quan;Lin Nan(Yue yang Meteorological Office of Hunan Province,Yueyang 414000)
出处
《应用气象学报》
CSCD
北大核心
2020年第3期328-338,共11页
Journal of Applied Meteorological Science
基金
湖南省气象局2016年重点科研课题(XQKJ16A003)
湖南省气象局2018年预报员专项(XQKJ18C007)。
关键词
扁山水龙卷
高空辐散
边界层中气旋
强烈抽吸作用
Bianshan waterspout
high-altitude divergence
mesocyclones in the boundary layer
strong pumping and suction
