Mesocyclone Evolution and Tornadogenesis: Some Observations
Mesocyclone Evolution and Tornadogenesis: Some Observations
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中气旋演化和龙卷发生：一些观察
DOI：
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发表时间：
1978
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影响因子：
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通讯作者：
E. Brandes
中科院分区：
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作者：
E. Brandes
在产生龙卷风的雷暴中，中气旋上升气流沿着汇聚和气旋切变的边界形成，这些边界将进入风暴前象限和后风暴象限的气流分开。最大切向气流位于环带风带中，平均半径小于3公里(取决于发展阶段)，在热带风暴发生期间在地面附近加强。在整个增强期间，集中在云底或云底以下的强流入保持不变。在龙卷风阶段，母体中环流表现出明显的“破裂”，即从单胞轴向双胞流结构的转变。在这一关键时期，细长的中气旋核心内可能出现小涡，一些可能变成龙卷风和/或发展成大比例。龙卷风的消散可能是由于主要中气旋水平轴的气旋旋转造成的，它扼杀了进入龙卷风的空气供应，使龙卷风与主上升气流分离。另一个明显的消散机制是龙卷风的消散。
Abstract Updraft mesocyclones in tornado-producing thunderstorms form along convergent and cyclonically sheared boundaries that separate inflow air entering forward and rear storm quadrants. Maximum tangential flow resides in girding wind bands, averaging usually less than 3 km in radius (depending upon the development stage), that strengthen near ground during toradogenesis. Strong inflow, concentrated at or below cloud base, is maintained throughout the intensification period. During the tornadic phase the parent mesocirculation exhibits an apparent “breakdown", i.e., a transition from single-cell to two-cell axial flow structure. At this critical period small eddies may appear within an elongated mesocyclone core and some may become tornado and/or grow to large proportions. Tornado dissipation may result from cyclonic rotation of the major mesocyclone horizontal axis which chokes the supply of inflow air and detaches the tornado from the principal updraft. Another apparent mechanism for dissipation inv...