Shi YunLong, Yang DeZhou, Feng XingRu, Qi JiFeng, Yang HongWei, Yin BaoShu
School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing, China.
Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
Sci Rep. 2018 Jul 4;8(1):10106. doi: 10.1038/s41598-018-28465-z.
Oceanic mesoscale eddies are common, especially in areas where zonal currents with meridional shear exists. The nonlinear effects complicate the analysis of mesoscale eddy dynamics. This study proposes a solitary (eddy) solution based on an asymptotic expansion of the nonlinear potential vorticity equation with a constant meridional shear of zonal current. This solution reveals several important consequences. For example, cyclonic (anticyclonic) eddies can be generated by the negative (positive) shear of the zonal current. Furthermore, the meridional structure of an eddy is asymmetrical, and the center of a cyclonic (anticyclonic) eddy tilts poleward (equatorward). Eddy width is inversely proportional to shear intensity. Eddy phase speed is proportional to shear intensity and the wave amplitude, and their spatial distribution show band-like pattern as they propagate westward. This nonlinear solitary solution is an extension of classical linear Rossby theory. Moreover, these findings could be applied to other areas with similar zonal current shear.
海洋中尺度涡旋很常见，尤其是在存在具有经向切变的纬向流的区域。非线性效应使中尺度涡旋动力学的分析变得复杂。本研究基于具有纬向流恒定经向切变的非线性位涡方程的渐近展开提出了一个孤立（涡旋）解。该解揭示了几个重要结果。例如，气旋（反气旋）涡旋可由纬向流的负（正）切变产生。此外，涡旋的经向结构是不对称的，气旋（反气旋）涡旋的中心向极地方向（向赤道方向）倾斜。涡旋宽度与切变强度成反比。涡旋相速度与切变强度和波幅成正比，并且它们的空间分布在向西传播时呈带状模式。这种非线性孤立解是经典线性罗斯比理论的扩展。此外，这些发现可应用于其他具有类似纬向流切变的区域。
