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首页> 外文期刊>Journal of Physical Oceanography >Internal Gravity Wave Emission in Different Dynamical Regimes
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Internal Gravity Wave Emission in Different Dynamical Regimes

机译：不同动力条件下的内部重力波发射

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We aim to diagnose internal gravity waves emitted from balanced flow and investigate their role in the downscale transfer of energy. We use an idealized numerical model to simulate a range of baroclinically unstable flows to mimic dynamical regimes ranging from ageostrophic to quasigeostrophic flows. Wavelike signals present in the simulated flows, seen for instance in the vertical velocity, can be related to gravity wave activity identified by frequency and frequency-wavenumber spectra. To explicitly assign the energy contributions to the balanced and unbalanced (gravity) modes, we perform linear and nonlinear modal decomposition to decompose the full state variable into its balanced and unbalanced counterparts. The linear decomposition shows a reasonable separation of the slow and fast modes but is no longer valid when applied to a nonlinear system. To account for the nonlinearity in our system, we apply the normal mode initialization technique proposed by Machenhauer in 1977. Further, we assess the strength of the gravity wave activity and dissipation related to the decomposed modes for different dynamical regimes. We find that gravity wave emission becomes increasingly stronger going from quasigeostrophic to ageostrophic regime. The kinetic energy tied to the unbalanced mode scales close to Ro(2) (or Ri(-1)), with Ro and Ri being the Rossby and Richardson numbers, respectively. Furthermore, internal gravity waves dissipate predominantly through small-scale dissipation, which emphasizes their role in the downscale energy transfer.
机译：我们旨在诊断平衡流发出的内部引力波，并研究它们在能量向下传递中的作用。我们使用理想化的数值模型来模拟一系列的斜压不稳定流，以模拟从变营养流到准营养营养流的动力学机制。存在于模拟流中的波状信号，例如以垂直速度看，可以与由频率和频率波数谱识别的重力波活动有关。为了将能量贡献明确分配给平衡和不平衡（重力）模式，我们执行线性和非线性模态分解，以将完整状态变量分解为其平衡和不平衡的对应变量。线性分解显示了慢速模式和快速模式的合理分离，但当应用于非线性系统时不再有效。为了解决系统中的非线性问题，我们应用了Machenhauer于1977年提出的正常模式初始化技术。此外，我们还评估了重力波活动的强度以及与不同动力状态下的分解模式相关的耗散。我们发现，重力波的发射从准营养型到非营养型变得越来越强。与不平衡模式相关的动能的尺度接近Ro（2）（或Ri（-1）），其中Ro和Ri分别是Rossby和Richardson数。此外，内部引力波主要通过小规模的消散而消散，这强调了它们在下层能量传递中的作用。

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