Inertia-gravity-wave scattering by three-dimensional geostrophic turbulence
Inertia-gravity-wave scattering by three-dimensional geostrophic turbulence
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三维地转湍流的惯性重力波散射
DOI：
10.1017/jfm.2021.205
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发表时间：
2021
影响因子：
3.7
通讯作者：
J. Vanneste
中科院分区：
文献类型：
--
作者：
M. Savva;H. A. Kafiabad;J. Vanneste
摘要在大气和海洋的旋转分层流中，重力惯性波（IGW）常与地转平衡湍流共存。这种流动的平流和折射导致波散射，在位置波数相空间中重新分配IGW能量。我们给出了一个详细的描述，这个过程中推导出的IGW相空间能量密度的演变动力学方程。推导依赖于小的Rossby数表征的地转流，这被视为一个随机场与已知的统计，使空间尺度分离的假设，并忽略波-波相互作用。它扩展了以前的工作局限于近惯性波，正压流或波比流尺度短得多。动力学方程描述的能量转移，被限制到IGW具有相同的频率，作为一个结果的时间尺度之间的分离波和流。我们制定的动力学方程上的恒定频率的表面-一个双锥波数空间-使用极球坐标，我们研究的形式，涉及的两个散射截面，量化IGW之间的能量转移，分别相同和相反的垂直传播方向。动力学方程捕获了水平各向同性和散射导致的跨尺度能量级联。我们把注意力集中在后者，以评估直接模拟的三维Boussinesq方程的动力学方程的预测，找到良好的协议。
Abstract In rotating stratified flows including in the atmosphere and ocean, inertia-gravity waves (IGWs) often coexist with geostrophically balanced turbulent flows. Advection and refraction by such flows lead to wave scattering, redistributing IGW energy in the position–wavenumber phase space. We give a detailed description of this process by deriving a kinetic equation governing the evolution of the IGW phase-space energy density. The derivation relies on the smallness of the Rossby number characterising the geostrophic flow, which is treated as a random field with known statistics, makes no assumption of spatial scale separation, and neglects wave–wave interactions. It extends previous work restricted to near-inertial waves, barotropic flows or waves much shorter than the flow scales. The kinetic equation describes energy transfers that are restricted to IGWs with the same frequency, as a result of the time scale separation between waves and flow. We formulate the kinetic equation on the constant-frequency surface – a double cone in wavenumber space – using polar spherical coordinates, and we examine the form of the two scattering cross-sections involved, which quantify energy transfers between IGWs with, respectively, the same and opposite directions of vertical propagation. The kinetic equation captures both the horizontal isotropisation and the cascade of energy across scales that result from scattering. We focus our attention on the latter to assess the predictions of the kinetic equation against direct simulations of the three-dimensional Boussinesq equations, finding good agreement.
地转湍流引起的惯性重力波的扩散
影响因子：
3.7
作者：
Kafiabad H
通讯作者：
Kafiabad H
非定常流引起的波的频率扩散
影响因子：
3.7
作者：
Dong, Wenjing;Bühler, Oliver;Smith, K. Shafer
通讯作者：
Smith, K. Shafer
DOI：
10.48550/arxiv.1804.06347
发表时间：
2018
期刊：
--
影响因子：
--
作者：
Savva M
通讯作者：
Savva M