中尺度涡旋调制东海黑潮入侵的关键动力学机制研究

Abundant mesoscale eddies exist in the Northwestern Pacific. The ones which arrive at east of Kuroshio not only has an impact on the Kuroshio itself, but also modulate its intrusion onto the East China Sea (ECS) shelf and produce a direct effect on the coastal circulation and biological environment of ECS. Previous studies have demonstrated that both the Kuroshio inertia and eddy-induced potential vorticity flux could make a contribution to the Kuroshio intrusion, but the dominant factor and the underlying dynamic mechanism still remain unclear. This study tries to explore this science question as follows. Based on the latest observations, high-resolution reanalysis data, and three-dimensional numerical modeling of the single mesoscale eddy-Kuroshio interaction, the response of Kuroshio to the large scale wind field change and mesoscale eddy will be analyzed to represent the special structural change of Kuroshio modulated by the mesoscale eddy. With model sensitivity experiments, the contributions of Kuroshio volume transport and structural changes will also be investigated to discuss the dominant reason of intrusion. The characteristic of potential vorticity budget of Kuroshio and its intrusion process will be analyzed to reveal the key dynamic mechanism responsible for the eddy induced Kuroshio intrusion. The resultss of this project will be a further supplement to the theory of the water exchange between the ECS shelf and Kuroshio, and provide the theoretical and observational foundation for the improvement of the capacity of the ECS dynamic environment prediction.

西北太平洋分布着大量的中尺度涡旋，抵达黑潮东侧时不仅会影响黑潮，还能够调制黑潮对东海陆架的入侵，直接影响中国近海的环流输运和生态系统响应。前人研究表明，在中尺度涡旋作用黑潮的过程中，惯性效应和涡旋的位涡通量强迫对黑潮入侵均有贡献，然而主导因素及其中的动力机制仍不清楚。针对该问题，本项目拟结合最新的观测和高分辨率的再分析资料，借助单一涡旋作用黑潮的三维数值模型，对比分析黑潮响应大尺度风场变化和中尺度涡旋的三维空间特征，给出中尺度涡旋引起的黑潮结构的特殊改变；通过敏感验性实验分析黑潮流量和结构改变对入侵的贡献，探讨涡旋作用过程中引起入侵改变的主要因素；分析黑潮及其入侵陆架过程的位涡收支特征，揭示中尺度涡旋调制黑潮入侵的关键动力学机制。本项目的科研成果将进一步补充东海黑潮与陆架水交换的理论体系，为中国近海的动力环境预报能力的提升提供一定的观测和理论依据。

中尺度涡旋对黑潮的影响及其在跨陆架物质和能量交换中的作用日益显著，其中的特征规律和动力机制是重要的科学问题。本项目基于观测资料、再分析资料和数值模拟，对中尺度涡旋特征及其作用黑潮的过程和动力机制进行了细致研究，主要研究成果有：首先，相对于前人提出的瑞利分布，发现大洋中的中尺度涡旋特征变量的概率密度分布更近似于对数正态分布，且不依赖于中尺度涡旋探测方法；其次，提出了大洋中尺度涡旋在台湾以东海域对黑潮强度季节变化的贡献，在夏季增强黑潮，在冬季减弱黑潮，并指出中尺度涡旋源地的副热带逆流的季节变化是中尺度涡旋极性季节变化的主要原因；第三，对台湾东北处中尺度涡旋引起的黑潮入侵变化做出了定量化估算，并阐明了涡旋的位涡通量输运是中尺度涡旋调节黑潮入侵的主要动力学机制，这部分工作在国际顶级期刊Journal of Geophysical research: Oceans期刊发表。本项目的科研成果完善了中尺度涡旋特征规律的认知，量化了中尺度涡旋对黑潮入侵的影响，补充了东海黑潮与陆架水交换的理论体系，促进了我国近海水文结构特征和环流变化规律的深入了解。