黑潮入侵南海的可预报性及适应性观测研究

The Kuroshio plays a key role in the exchange of water mass and the transport of energy between the South China Sea (SCS) and the weatern Pacific Ocean by its invasion to the SCS through the Luzon Strait, which has significant impacts on the formation of water mass and the thermodynamic processes in the SCS. Howerver, both the path and strenth of the Kuroshio intrusion have large seasonal and interannual/interdecadel variability, leading to large uncertainties in simulation and prediction of the intrusion using state-of-the-art numerical models. In this study, we explore the first class of predictability of the Kuroshio intrusion using the method of Conditional Non-linear Optimal Perturbation (CNOP). Upon revealing the characteristic of the spatial distribution and temporal evolution of the non-linear optimal perturbation causing the variation of path and strenth of the intrusion, we design an optimal observing scheme and conduct a set of Observation System Simulation Experiments (OSSE) based on the 4-dimension variational data assimilation (4DVAR) approach, which could provide the scientific evidence and reasonable suggestion for the potential observing system deployed in the area in the future.All of these could help to improve the skills of regional ocean circulation models in simulating and predicting the Kuroshio intrusion to the SCS.

黑潮通过吕宋海峡对南海的入侵在南海与西太平洋之间的水团交换、能量输送等扮演着关键角色，对南海内部的水团构成、热力和动力过程有重要影响。而黑潮入侵（南海）的路径及强度又存在较大的季节和年际年代际变率，导致目前海洋环流模式对其模拟和预报存在较大的不确定性。本项目拟利用条件非线性最优扰动（CNOP）方法探讨黑潮入侵（南海）的第一类可预报性问题，揭示导致其路径及强度变化的非线性最优扰动的时空分布与演变特征，并据此设置最优的观测布点方案，然后进行基于四维变分同化方法的观测系统模拟试验，为未来可能实施的该海区观测网络提供科学依据和合理建议，以提高区域海洋环流数值模式对黑潮入侵（南海）的模拟和预报技巧。

通过三维海洋模式及其伴随模式，构建了以黑潮入侵南海为关键区域的目标观测模拟系统，为研究黑潮入侵南海的观测布点方案提供决策依据；利用三维海洋模式，结合能量收支分析方法估算的南海跨等密度面潮致（内潮）混合系数的空间分布。在此基础上分析了潮致混合对黑潮入侵南海深层水体输运的影响。利用形成的30年模式产品分析了季节尺度上黑潮入侵对可预报性；并通过敏感性试验证明了对于区域海洋模式在季节尺度上边界场和初始场对黑潮入侵模拟的影响是主要的，而风场的影响较小。在此基础上，根据CNOP的空间分布及随时间演变特征，设置针对黑潮入侵南海的最优观测布点方案，并进行不同观测布点的观测系统模拟试验（OSSE），结果表明了CNOP敏感区对黑潮预报影响最大，该目标观测系统能有效获取黑潮入侵南海流量预报的敏感区。相关研究成果达到了预期的研究目标。