Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations
Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations
复制标题
下沉气流输送循环引起的龙卷风：理想化数值模拟
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
E. Rasmussen
中科院分区：
文献类型：
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作者：
P. Markowski;J. Straka;E. Rasmussen
摘要 进行了理想化的数值模拟，其中启动了无雨的轴对称、潮湿、旋转上升气流，然后通过降水载荷施加了下降气流。这些实验旨在模拟超级单体上升气流，该上升气流最初在高空旋转，然后形成下降气流并在后侧雨幕下降。在理想化的模拟中，雨幕和下沉气流是环形的，而不是通常观察到的钩形。下降气流将角动量输送到地面，角动量最初在高空最大，在地面为零。一旦到达地面，富含循环的空气就会在上升气流下方汇聚，形成龙卷风。龙卷风的强度和持续时间取决于角动量输送下降气流的热力学特征，而其对环境低层相对湿度和雨幕降水特征敏感。对于大的低水平相对湿度和...
Abstract Idealized numerical simulations are conducted in which an axisymmetric, moist, rotating updraft free of rain is initiated, after which a downdraft is imposed by precipitation loading. The experiments are designed to emulate a supercell updraft that has rotation aloft initially, followed by the formation of a downdraft and descent of a rain curtain on the rear flank. In the idealized simulations, the rain curtain and downdraft are annular, rather than hook-shaped, as is typically observed. The downdraft transports angular momentum, which is initially a maximum aloft and zero at the surface, toward the ground. Once reaching the ground, the circulation-rich air is converged beneath the updraft and a tornado develops. The intensity and longevity of the tornado depend on the thermodynamic characteristics of the angular momentum-transporting downdraft, which are sensitive to the ambient low-level relative humidity and precipitation character of the rain curtain. For large low-level relative humidity an...