苏禄海环流年际变化及与南海东部环流相关性研究

Sulu Sea (SS) is located in the southeast of the South China Sea (SCS). It connects with the SCS via the Mindoro Strait and the Balabac Strait. The water exchange via these two straits, especially the Mindoro Strait, probably plays an important role in the circulation in the SS and the eastern SCS. Our preliminary studies have revealed the seasonal variation of the surface SS circulation and its dynamical mechanism. A strong correlation between the circulation changes in the SS with that in the SCS has also been found. In this project, we are going to collecte the satellite remote sensing data and in-situ observational data. The Cyclostationary Empirical Orthogonal Functions (CSEOF) will be used to analyze the model and time series of the inter-annual variability of the circulation in the SS. Then a high resolution nested grids Oceanic General Circulation Model (OGCM) will be employed to simulate the circulation in the SS and both the correlation between the circulation in the eastern SCS and that in the SS and the impact of the water exchange on the eastern SCS circulation will be discussed. Ultimately we try to reveal the relative dynamical mechanism according to the theoretical analysis and model experiments. This study will deepen the knowledge of the inter-annual variability and dynamical mechanism of the circulation and climates in the SCS, which is both critical to the physical oceanography and regional oceanology.

苏禄海位于南海东南部，经民都洛海峡和巴拉巴克海峡与南海相连接。经由这两个海峡（特别是民都洛海峡）的水交换可能对苏禄海和南海东部环流产生重要的影响。申请者参与的前期研究揭示了苏禄海表层环流季节变化及其影响因素，且发现苏禄海环流变化与南海环流有较强的相关关系。本项目以研究苏禄海年际变化特征为中心，通过搜集该海域卫星观测数据和水文资料，使用CSEOF方法分析苏禄海年际变化模态特征和变化规律；进而利用高分辨嵌套网格数值模式模拟苏禄海环流，探讨苏禄海环流与南海东部环流的相关性，分析其水交换对南海东部环流的影响；最后通过理论分析和模式实验揭示其中的动力机制。本项目将有助于深化认识苏禄海环流与南海东部环流的年际尺度变异和相互作用、了解其有关动力机制，对预测南海及其周边海洋气候环境变异有着重要的物理海洋学和区域海洋学意义。

本项目基于多年卫星遥感高度计数据，首先对苏禄海涡旋进行了统计分析，研究了苏禄海涡旋的特征。研究表明苏禄海气旋（反气旋）涡倾向于将苏禄海南部的高涡动能带向东北（西北）方向。之后利用MITgcm模拟研究了吕宋冷涡的时空变化和动力机制，发现在吕宋岛以西上层和下层在不同时间会分别生成两个冷涡，上层冷涡主要由风应力旋度生成，而下层冷涡则来自于吕宋海峡向西传播的冷涡。我们进一步使用多年卫星高度计数据研究了冬季南海东部涡旋的年际变化，发现吕宋冷涡在El Niño（La Niña）年会减弱（增强），风应力旋度的年际变化可能是这种不同的主要原因。另外，民都洛海峡输运的年际变化也可能对民都洛岛西北和西边的暖涡和冷涡位置和强度产生影响。最后，课题组还使用数值模式对黑潮入侵南海进行了被动示踪物模拟研究及南海北部季节性涡度收支研究。