王秀明,俞小鼎. 2019. 热带一次致灾龙卷形成物理机制研究[J]. 气象学报, (0):-, doi:10.11676/qxxb2019.031
热带一次致灾龙卷形成物理机制研究
Study on the tornadogenesis of a tropical severe tornado
投稿时间:2018-02-22  修订日期:2018-05-11
DOI:10.11676/qxxb2019.031
中文关键词:  中气旋龙卷  龙卷生成  出流边界  海风锋
英文关键词:mesocyclonic tornado  tornadogenesis  outflow boundary  sea-breeze
基金项目:国家自然科学基金
作者单位E-mail
王秀明 中国气象局干部培训学院 wangxm@cma.gov.cn 
俞小鼎 中国气象局干部培训学院 xdyu1962@126.com 
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中文摘要:
      初始风暴在文昌附近向西传播,而同时海口风暴亦由海风锋触发并向东移动,两风暴下沉气流导致的出流相遇在海风锋辐合线上,触发了龙卷母云体。龙卷初始涡旋在低层两风暴出流相遇的切变辐合线上形成,当初始涡旋与其上方深厚且强烈的上升气流叠置时,拉伸作用大大加强了垂直涡度,使得龙卷形成。深厚的强上升气流有三个来源:对流风暴的出流边界(outflow boundaries)相遇形成的辐合抬升;环境正浮力造成的对流单体内强上升气流,还可能与中高层强中气旋强迫的扰动低压有关。龙卷形成过程中,中高层强中气旋位于6-9 km高空并向上发展,龙卷初始涡旋先于龙卷母云体出现且比一般微气旋尺度大,伸展至更高的高度,属于非典型中气旋龙卷(或非典型超级单体龙卷)。此次热带强龙卷出现在弱的大尺度系统强迫的天气背景下,水平风垂直切变弱,海风锋、出流边界等边界层中β尺度辐合线边界在龙卷形成过程可能起决定性作用。
英文摘要:
      Hainan island was suffered by a wide spread Severe wind on 5 June 2016,but the damage and death mainly caused by an EF2 tornado. A movie record the tornado funnel and dust devil , the Haikou Doppler weather radar documented the tornadic storm 50km away,and surface AWS are ten minutes interval. It is possible to study the tornadogenesis. The first storm are initiated by sea breeze, and it move to east to the sea following the surrounding wind. It is a single cell storm. When the convergence of see breeze intensified the PBL lifting, the storm turn back to west to the island, for new convection initiated along the see breeze. That was the Wenchang Multicellular storm. The outflow of the Wenchang storm moved to the west, and the outflow of Haikou storm which trigged along the Haikou see breeze moved towards east at the same time, the tornado vortex formed where two outflow boundaries intersected. The stretching of the deep strong updraft above the tornado vortex is the main physical process of tornadogenesis. There are three factors contributed to the extremely strong lifting, the outflow boundary intersection, the ambiance large positive buoyancy and the vertical perturbation pressure gradient associated with the low pressure induced by high level strong mesocylone. The mesocyclone of supercell was located at 6-9km above ground, it was extraordinary high. The tornado was not formed by the desending of high level mesocyclone, and there is no significant supercellular rear flankling downdraft (RFD) when tornadogenesis, so it was not similar to classic supercellular tornado. It was different with the non-supercellular(non-mesocylonic)tornado either. The high level mesocyclone contributed to the tornadogenersis, the TVS extended to 6km for the high mesocyclone and positive buoyancy. The low-level vortex was not misocylone(less than 4km wide, less than 2km high). Deep and extremely strong updraft velocity was the main factor for EF2 tornado and it’s sustained. It was suggested to classify it as an non-typical mesocyclonic tornado. This was an tropical tornado under weak synoptical-scale force, and it was not a tropical cyclone tornado, the vertical wind shear was weak, the sea-breeze and the storm generated outflow boundary played a critical role on the tornadogenesis.
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