Topographic Waves Generated by a Transient Wind
Topographic Waves Generated by a Transient Wind
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瞬变风产生的地形波
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
H. Teitelbaum
中科院分区：
文献类型：
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作者：
F. Lott;H. Teitelbaum
摘要线性山波的概念通常等同于稳态驻波。这本质上意味着，在没有耗散和零级风的情况下，山波的绝对水平相速度为零，其动量通量廓线与高度和时间无关。本文研究了线性非定常山体重力波的产生。入射流是瞬变的，在给定时间从零开始，在有限时间后返回到零。地形是单一的水平调和。波动的不稳定性部分是由于它们在含时平均流中传播过程中相速度的时间变化。当风停止时，存在的大多数波的相速度几乎与最大风相反。出于这个原因，山波可以在零均风层中传播。波场的暂态结构还来自于地震波振幅的时间变化。
Abstract The concept of linear mountain waves is generally equated with steady-state stationary waves. This essentially means that the absolute horizontal phase velocity of mountain waves is zero and that their momentum flux profile is independent of height and time in the absence of dissipation and zero-level wind. This paper investigates the generation of linear unsteady mountain gravity waves. The incident flow is transient, starting from zero at a given time and returning to zero after a finite time. The topography is a single horizontal harmonic. The unsteadiness of the waves is due partly to the temporal change of their phase velocity, which takes place during their propagation in the time-dependent mean flow. When the wind ceases, most of the waves present have a phase velocity nearly opposite to the maximum wind. For this reason, mountain waves can propagate through levels of zero mean wind. The transient structure of the wave field also comes from the temporal change of the amplitude of the groun...