Interaction of near-inertial waves with an anticyclonic vortex
Interaction of near-inertial waves with an anticyclonic vortex
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DOI：
10.1175/jpo-d-20-0257.1
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发表时间：
2020-10
影响因子：
3.5
通讯作者：
H. A. Kafiabad;J. Vanneste;W. Young
中科院分区：
文献类型：
--
作者：
H. A. Kafiabad;J. Vanneste;W. Young
反气旋涡旋集中并捕获近惯性波，从而在涡旋核心内提高近惯性能量水平。这个过程的某些方面，包括非线性修改的涡波，被困近惯性本征模式的存在解释。这些涡旋本征模容易被水平尺度远大于涡旋半径的初始波激发。我们研究这个过程中使用的波平均模型的近惯性动力学和比较其理论预测与数值解的三维Boussinesq方程。在线性近似中，该模型预测的本征模频率和空间结构，和近惯性波能量签名，其特征在于由一个近似的时间周期性，方位角不变的图案。波平均模型表示通过波引起的对位涡的贡献的波对涡的非线性反馈，该位涡与波的动能密度的拉普拉斯算子成比例。当考虑到这一点时，模态频率被预测为随着初始激励的能量线性增加。线性和非线性预测都令人信服地同意与Boussinesq的结果。
Anticyclonic vortices focus and trap near-inertial waves so that near-inertial energy levels are elevated within the vortex core. Some aspects of this process, including the nonlinear modification of the vortex by the wave, are explained by the existence of trapped near-inertial eigenmodes. These vortex eigenmodes are easily excited by an initialwave with horizontal scale much larger than that of the vortex radius. We study this process using a wave-averaged model of near-inertial dynamics and compare its theoretical predictions with numerical solutions of the three-dimensional Boussinesq equations. In the linear approximation, the model predicts the eigenmode frequencies and spatial structures, and a near-inertial wave energy signature that is characterized by an approximately time-periodic, azimuthally invariant pattern. The wave-averaged model represents the nonlinear feedback of the waves on the vortex via a wave-induced contribution to the potential vorticity that is proportional to the Laplacian of the kinetic energy density of the waves. When this is taken into account, the modal frequency is predicted to increase linearly with the energy of the initial excitation. Both linear and nonlinear predictions agree convincingly with the Boussinesq results.