The internal structures of mesoscale eddies are variable due to different generation mechanism, spatiotemporal scale, and movement characteristics. Based on the principle of data assimilation, this study provided a new approach for constructing the eddy real-time internal structure using the gradient-dependent optimal interpolation (OI) method. Three eddy cases with different types and locations were selected to validate the construction results. The reliability of construction was evaluated by satellite observation, in-situ comparisons, and contrast with the numerical output. The results showed that the real-time geostrophic current characters were basically consistent with the surface and deep current (observed by satellite and acoustic doppler current profiler, ADCP). The density features exhibited by constructed results (eddy centers, mean radii, and variation tendency) were similar to the expendable conductivity-temperature-depth (XCTD) survey data and numerical output. Compared to the composite structure, the real-time structures represented more small or mesoscale fluctuations. During eddy cases evolution, the mean radii at the same depth first increased and then decreased. The horizontal scale, influence depth, and internal stability of an anticyclonic eddy with low-latitude were more powerful than the other two eddy cases owing to the domination of warm water in the Kuroshio extension region. The results indicated that the gradient-dependent OI was a hopeful technique for representing the real-time internal features during eddy evolution.

中文翻译：

---

黑潮-亲潮交汇区基于梯度相关OI的涡流实时结构实验构建

由于产生机制、时空尺度和运动特征的不同，中尺度涡旋的内部结构也存在差异。基于数据同化原理，本研究为利用梯度相关最优插值（OI）方法构建涡流实时内部结构提供了一种新方法。选取了3个不同类型、不同位置的涡流工况来验证施工结果。通过卫星观测、现场对比、数值输出对比等方式对施工可靠性进行评估。结果表明，实时地转流特征与地面和深部海流（卫星和声多普勒海流剖面仪（ADCP）观测）基本一致。构造结果（涡流中心、平均半径和变化趋势）表现出的密度特征与消耗性电导率-温度-深度（XCTD）测量数据和数值输出相似。与复合结构相比，实时结构代表了更小的或中尺度的波动。在涡情况演化过程中，同一深度的平均半径先增大后减小。由于黑潮延伸区暖水占主导地位，低纬度反气旋涡的水平尺度、影响深度和内部稳定性均比其他两个涡实例更强。结果表明，梯度相关的 OI 是表示涡旋演化过程中实时内部特征的一种有希望的技术。