A Linear Model of Back-Sheared Flow over an Isolated Hill in the Presence of Rotation
A Linear Model of Back-Sheared Flow over an Isolated Hill in the Presence of Rotation
复制标题
存在旋转时孤山上反剪切流的线性模型
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
G. Shutts
中科院分区：
文献类型：
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作者：
G. Shutts
线性化的解决方案推导出的情况下，恒定（负）剪切流在一个孤立的，圆对称的山，并评估三个特征波制度。特别感兴趣的是所产生的惯性重力波场的三维结构，其接近两个水平中的较低水平，其中固有频率的大小等于科里奥利参数-惯性临界水平。与等效非旋转问题相反，临界水平高度是表示扰动的每个傅立叶模式的水平波数的函数。此外，波场，其中包括一个下游的惯性波的火车，表现出方位角的不对称性的流动方向。当山附近的Rossby数小于1时，波的响应由瞬逝扰动和从山水平辐射的中性斜压背风波组成。这些也显示出一些横流不对称性，尽管与惯性重力波场的情况相反。波应力的谱分布被发现是对称的流动方向，和总应力平均在有限域面积随高度衰减波伪动量进行下游的准惯性波的形式。
Linearized solutions are derived for the case of constant (negative) shear flow over an isolated, circularly symmetric hill and are evaluated for three characteristic wave regimes. Of particular interest is the threedimensional structure of the resulting field of inertia‐gravity waves near the lower of two levels where the magnitude of the intrinsic frequency is equal to the Coriolis parameter—the inertia critical levels. In contrast to the equivalent nonrotating problem, the critical level height is a function of the horizontal wavenumber for each Fourier mode representing the disturbance. Furthermore the wave field, which consists of a downstream train of inertia waves, exhibits an azimuthal asymmetry about the direction of the flow. When the Rossby number near the mountain is less than unity the wave response consists of an evanescent disturbance and a pattern of neutral baroclinic lee waves that radiate horizontally away from the hill. These too show some cross-flow asymmetry, though in the opposite sense to that found with the inertia‐gravity wave field. The spectral distribution of the wave stress is found to be symmetric about the flow direction, and the total stress averaged over the finite domain area decays with height as wave pseudomomentum is carried downstream in the form of quasi-inertial waves.