Energy cascade in the Garrett–Munk spectrum of internal gravity waves
Energy cascade in the Garrett–Munk spectrum of internal gravity waves
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DOI：
10.1017/jfm.2023.862
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发表时间：
2023-05
影响因子：
3.7
通讯作者：
Yue Wu;Yulin Pan
中科院分区：
文献类型：
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作者：
Yue Wu;Yulin Pan
摘要本文通过对波动方程中碰撞积分的数值计算，研究了重力内波Garrett-Munk谱中由于波三波相互作用引起的谱能量转移。我们的数值计算建立在减少碰撞积分的共振流形上的水平各向同性频谱。我们直接计算了可用于海洋混合的下尺度能量通量，其值与细尺度参数化结果非常吻合。我们进一步将能量传递分解为不同机制的贡献，包括局部相互作用和三种类型的非局部相互作用，即参数亚谐波不稳定性、弹性散射（ES）和诱导扩散（ID）。通过对各机制作用的分析，我们解决了长期存在的两个悖论，即频率上的前向级联机制和GM 76谱的零ID通量。此外，我们的分析估计的贡献，每个机制的能量转移在每个光谱方向，并揭示了新的理解的重要性，本地相互作用和ES的能量转移。
Abstract We study the spectral energy transfer due to wave–triad interactions in the Garrett–Munk spectrum of internal gravity waves based on a numerical evaluation of the collision integral in the wave kinetic equation. Our numerical evaluation builds on the reduction of the collision integral on the resonant manifold for a horizontally isotropic spectrum. We evaluate directly the downscale energy flux available for ocean mixing, whose value is in close agreement with the finescale parameterization. We further decompose the energy transfer into contributions from different mechanisms, including local interactions and three types of non-local interactions, namely parametric subharmonic instability, elastic scattering (ES) and induced diffusion (ID). Through analysis on the role of each mechanism, we resolve two long-standing paradoxes regarding the mechanism for forward cascade in frequency and zero ID flux for the GM76 spectrum. In addition, our analysis estimates the contribution of each mechanism to the energy transfer in each spectral direction, and reveals new understanding of the importance of local interactions and ES in the energy transfer.