北太平洋副热带逆流的气候特征及形成机制的研究

Based on NCEP/NCAR assimilation data, SODA (Simple Ocean Data Assimilation) data，the output of the high-resolution Parallel Ocean Climate Model (POCM), TOPEX/POSEIDON-ERS altimetry data (T/P-ERS), using the 2.5 layer numerical model, the main feature of the Subtropical Countercurrent (STCC) and its seasonal and interannual variability, and their formation mechanism have been investigated. The STCC in the Northern Subtropical Pacific may be divided into two branches: one in the Northwestern Pacific (19o~27oN to the west of 170oE) and the other to the west of the Hawaii Islands (to the west of the 158oW) along 19o~20oN. The last one is stronger (weaker) in Summer (Winter). The first one is corresponding with thermal structure of upper layer well, and its formation and seasonal variation can be explained by subduction of subtropical mode water. Two mechanisms contribute to the formation of the eastward countercurrent to the west of Hawaii. First, the blocking effect of the Hawaiian Islands on the easterly trade winds generates a dipole of wind stress vorticity. This dipole of wind stress vorticity acts to create an eastward current jet to the west of the Hawaii Island, through the Sverdrup relation. Second, as the NEC impinges upon the Islands, westward-traveling "vortex streets" are generated in the ocean and act to intensify the eastward current to the west of the Hawaiian Islands. The research results published in international science publication , such as "Science" and "J. Geophysical Research", and guided the new study about the subtropical Atmosphere- Land -Ocean Interaction.

三十多年来，对北太平洋副热带逆流时空分布气候特征尚无统一认识，对其形成机制也无合理解释。本项目试图借助长达８年的卫星遥感资料和海洋观测资料，利用高分辨率海洋环流模式，依据１９９８年提出的新绕岛环流理论，掌握北太平洋副热带逆流的基本结构和季节、年际变化特征，揭示其形成机制，为较准确地预测副热带逆流和北太平洋海温异常奠定基础。