Abstract

Recently, it has been shown for the first time by observations that an anticyclonic mesoscale eddy can generate internal waves (wavelengths of 0.4 to 1 km) that carry energy away from the eddy. In the present study, we investigate a possible mechanism for generating internal waves near the edge of a submesoscale eddy. The study was motivated by airborne infrared imagery that shows curved thermal bands (wavelengths ∼70 m) near the edge of a 1-km-diameter cyclonic eddy. We hypothesize that these bands represent internal wave wakes generated by turbulent perturbations having scales of a few tens of meters that are advected along the eddy’s thermal perimeter. An analytical theory is developed to investigate this for an idealized perturbation advected by a circular current. Calculations show that, for a reasonable choice of parameter values, an internal wave wake develops around the eddy that has spiral-like phase lines resembling the orientations and wavelengths of the field observations. The general validity of our proposed mechanism should be verified with further studies.

摘要

最近，观测首次表明反气旋中尺度涡流可以产生内波（波长为 0.4 到 1 公里），将能量从涡流中带走。在本研究中，我们研究了在亚中尺度涡流边缘附近产生内波的可能机制。这项研究是由机载红外图像驱动的，该图像显示了直径 1 公里的气旋涡流边缘附近的弯曲热带（波长约 70 m）。我们假设这些带代表了由沿着涡流热周界平流的数十米尺度的湍流扰动产生的内部波尾流。开发了一种分析理论来研究由圆形电流平流的理想化扰动。计算表明，对于参数值的合理选择，内部波尾流围绕涡流发展，其具有类似于现场观测的方向和波长的螺旋状相位线。我们提出的机制的一般有效性应该通过进一步的研究来验证。