Wave Ducting in a Stratified Shear Flow over a Two-Dimensional Mountain. Part II: Implications for the Development of High-Drag States for Severe Downslope Windstorms
Wave Ducting in a Stratified Shear Flow over a Two-Dimensional Mountain. Part II: Implications for the Development of High-Drag States for Severe Downslope Windstorms
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二维山上层状剪切流中的波导。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Yuh
中科院分区：
文献类型：
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作者：
Ting;Yuh
本研究发现，早期关于严重下坡风的研究之所以存在差异，是因为使用了临界水平高度（zc）而不是低层均匀流层深度（z1）作为确定大阻力状态发生的最佳条件的指标。可以确定，一旦破波发生，就会在较低的均匀风层中诱导出一个临界水平，并形成有利于导波的流动构型，从而决定了反射波的相位。在地形跟踪坐标（σ1）中，确定了具有均匀静态稳定性和基态临界水平的二维非旋转流动的高、低阻力状态流型，并将其作为无量纲山高(h)、理查德森数（Ri）和无量纲z1的函数。结果表明：1)当σ1一定时，高阻态临界h随Ri的增加而增加；
Abstract In this study, it is found that the discrepancies among earlier studies of severe downslope windstorms are caused by the use of the critical level height (zc), instead of the low-level uniform flow–layer depth (z1), as an indicator to determine the optimal conditions for the occurrence of high-drag states. It is determined that once the wave breaking occurs, it induces a critical level and establishes a flow configuration favorable for wave ducting in the lower uniform wind layer, which determines the phase of reflected waves. Flow regimes of high- and low-drag states for a two-dimensional, nonrotating flow with uniform static stability and a basic-state critical level over a mountain were also determined as functions of nondimensional mountain height (h), Richardson number (Ri), and nondimensional z1 in the terrain-following coordinates (σ1). The authors found that 1) the critical h for high-drag state increases as Ri increases when σ1 is fixed, 2) the critical h for high-drag state increas...