Study on three dimensional structure of high and mid-latitude ocean circulation under idealized situation

利用理想化的OGCM进行了数值试验，研究了海洋环流的三维结构。模型海洋由风和表面浮力共同驱动，并包括了南半球的深水形成。结果表明，东部边界是次表层水的来源：东部边界俯冲的水沿边界向赤道方向流动，然后向西进入大洋内陆区。这种向赤道方向的流动是在没有风力的情况下发生的。基于位涡平衡的分析表明，垂直密度扩散是产生这一流的重要因素。模型结果对垂直扩散的敏感性研究和基于线性模式的理论研究也证实了这一观点。此外，为了考虑海洋温跃层的变化，从理论上研究了2.5层通风温跃层模式中的线性行星波动力学。在描述了波的局部特性之后，讨论了波在海洋环流中的传播和海洋对大气作用力的响应。研究了有限波长对波长特性和稳定性的影响。

Numerical experiments using an idealized OGCM were carried out to investigate the three dimensional structure of ocean circulation. The model ocean was driven by both wind and surface buoyancy forcing, and deep water formation in the southern hemisphere was included. The results show that the eastern boundary is a source of subsurface water : the water subducted at the eastern boundary flows equatorward along the boundary and then turns westward into the oceanic interior region. This equatorward flow occurs without wind forcing. The analysis based on the potential vorticity balance suggests that the vertical density diffusion is important for generating this current. Sensitivity study of the model results to the vertical diffusion and a theoretical study based on a linear model were also carried out to confirm this idea.In addition to the above work, linear planetary wave dynamics in a 2.5-layer ventilated thermocline model was theoretically investigated to consider the oceanic thermocline variability. After describing the local properties of the waves, wave propagation in a oceanic gyre and oceanic response to atmospheric forcings were discussed. Effects of finite wave length on the wave properties and stabilities were also studied.