中国科学院海洋研究所机构知识库

中尺度涡旋是海洋环流的重要组成部分，其空间尺度通常在几千米到几百千米，时间尺度在几周到几个月。作为连接大尺度运动与小尺度运动的纽带中尺度涡旋对海洋中的物质、能量、热量等的传播与混合起着重要作用，同时对海洋中多尺度的运动、海洋生态、大气环境、以及气候变化等都有着十分重要的影响。本论文从欧拉以及拉格朗日两个角度分别对南海中尺度涡旋以及阿古拉斯涡旋进行了研究。欧拉方法以及拉格朗日方法在中尺度涡旋的研究上各有利弊，欧拉方法更适合研究涡旋的短期特征而拉格朗日方法对长期存在的涡旋以及涡旋对水体输运的研究上远胜欧拉方法。我们首先用欧拉方法对南海中尺度涡旋进行了统计研究，后着重研究了南海偶极子，讨论了南海偶极子的可预报性并首次对其进行经验预报，然后讨论了ENSO对南海偶极子的影响；接着介绍了拉格朗日非线性动力系统理论以及方法，并且将其应用在阿古拉斯涡旋的研究上，发现阿古拉斯涡旋并不像过去人们认为的那样携带高温高盐的阿古拉斯洋流水体横跨大西洋，能够跨越大西洋的阿古拉斯涡旋只携带了很少一部分的阿古拉斯洋流水体，其携带的大部分水体都来自于大西洋。同时针对阿古拉斯涡旋个例的研究表明作为超级连贯涡旋的阿古拉斯涡旋，其周围存在能够不断吸收非连贯水体的短期连贯环带，使得涡旋可以将周围的非连贯水体转为连贯水体而成长。并且发现阿古拉斯涡旋之所以能够长期保持连贯与其强动能边界密不可分。

Mesoscale eddy is an indispensable part of ocean circulation, with a typical spatial scale of several to hundreds kilometers and a time scale ranging from weeks to months. As a connection of the large ocean currents to small scale movements, mesoscale eddy plays an important role in transportation and mixing of mass, heat, energy, nutrition, etc in the ocean. Meanwhile it also has a great impact on multi-scale ocean movements, marine ecology, atmosphere condition, and climate change. This dissertation focuses on the study of mesoscale eddies, using both Eulerian and Lagrangian methods which both have their own inherent advantages and disadvantages. The Eulerian method is effective in analyzing short-term properties of the eddies while the Lagrangian method is much more competent when it comes to the study of long-existing eddies and ocean water transportation. First, we did a statistic study of mesoscale eddies in the South China Sea (SCS) followed by a predictivity study of the SCS dipole and discussed the impact of ENSO on the SCS dipole. Then the Lagrangian  nonlinear dynamical systems theory and methods are introduced which have been further applied on the detection of Agulhas rings. Unlike former studies, we found the water carried inside those long-existing Agulhas rings is actually formed largely from the Atlantic ocean water. Meanwhile our study focused on a specific long-existing Agulhas ring shows that the super coherent cores are surrounded by short-term coherent loops which can absorb incoherent water from turbulent surroundings and transform them into coherent water thus make the coherent structure to grow. We also found that the reason the Agulhas ring can stay coherent for more than a year can attribute to the shielding of the high-energetic boundary.