Abstract A fully calibrated and validated 3D hydrodynamic model is applied to the Baltic Sea to investigate the vortical structures in the Baltic Sea in the period 2000–2009. The novelty of the study is the detection and dynamics of large scale mesoscale vortices both in horizontal and vertical planes by using the instantaneous velocity vectors. This study provides some new insights into the type and dynamics of vortical structures in the Baltic Sea. In the horizontal plane, vortices with typical length and velocity scale of 5–12 km and 5–10 cm/s are present. They are of open type three-dimensional structures having two important features. They extend to 90% of the flow depth and have a clear periodicity of one to seven days. The vortices rotate both in clockwise and anti-clockwise directions. The baroclinic Rossby deformation radii are in the same range. The maximum numbers of mesoscale vortices are within the 15-m thick surface layer that diminishes towards the bottom layer. In the vertical planes, there is a multi-layered structure with the layer numbers varying from 2 to 4. Each layer is characterized by a set of distinct vortices. Taylor-Gortler type vortices appear within the surface layers. The middle flow layers are featured by distorted large-scale vortices. Boundary trapped vortices and large local circulation patterns feature the deeper bottom flow layers. There are two underlying mechanisms of vortex generation: one is shear layer instability of the Kelvin Helmholtz type and the other Taylor-Gortler. A conceptual general vortex model is proposed that applies to all basins of the Baltic Sea in vertical planes. Three types of structures are possible in the mixed layer, pycnocline, and the deep layer. In these are Taylor-Gortler vortices, mesoscale coherent structures, and trapped boundary vortices, respectively.

中文翻译：

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波罗的海涡旋结构动力学

摘要 将经过充分校准和验证的 3D 流体动力学模型应用于波罗的海，以研究 2000-2009 年期间波罗的海的涡旋结构。该研究的新颖之处在于通过使用瞬时速度矢量对水平和垂直平面中的大规模中尺度涡旋进行检测和动力学分析。这项研究为波罗的海涡旋结构的类型和动力学提供了一些新的见解。在水平面上，存在典型长度和速度尺度为 5-12 km 和 5-10 cm/s 的涡旋。它们是具有两个重要特征的开放式三维结构。它们延伸到水流深度的 90%，并且具有 1 到 7 天的明显周期性。漩涡以顺时针和逆时针方向旋转。斜压 Rossby 变形半径在相同的范围内。中尺度涡的最大数量位于 15 米厚的表层内，该表层朝向底层逐渐减少。在垂直平面上，有一个多层结构，层数从 2 到 4 不等。每一层都以一组不同的涡旋为特征。Taylor-Gortler 型涡流出现在表层内。中间流层以扭曲的大尺度涡流为特征。边界困涡和大型局部环流模式具有更深的底部流动层。涡流产生有两种基本机制：一种是 Kelvin Helmholtz 类型的剪切层不稳定性，另一种是 Taylor-Gortler。提出了一种适用于波罗的海所有盆地垂直平面的概念性一般涡流模型。混合层中可能存在三种类型的结构，pycnocline 和深层。其中分别是 Taylor-Gortler 涡、中尺度相干结构和被困边界涡。