Basic Research on Development of Ocan Prediction Models for Asian Marginal Seas

目前开发海洋预报模式的基础研究是由东京大学的海洋学家联合进行的，京都大学，九州大学，三重大学，与爱媛大学合作，特别强调NEAR GOOS区域。主要成果如下：建立了一个水平分辨率为1/18度的超高分辨率嵌套海洋模式，成功地模拟了黑潮的垂直结构和路径。该模型还解决了海洋潮汐。通过对模式结果的分析，阐明了斜压性和底起伏的联合作用（JEBAR）在九州岛西南海域黑潮东移中的重要作用，底扭矩的作用是将黑潮向更深区域推进。示踪实验表明，夏（冬）季对马海流中约50%（20%）的水团来自台湾海峡，50%（70%）来自黑潮，鄂霍次克海低位涡的外流是北太平洋中层水的来源之一。使用高分辨率非流体静力海洋模式，我们已经表明，潮汐混合形成的锋面斜压不稳定性引起的涡旋脱落在这一过程中发挥着至关重要的作用。鄂霍次克海的海水甚至渗透到四国海盆。RIAMINO海洋模式成功地用于日本海海流的后报实验。试验中采用的资料同化方法是基于卡尔曼滤波的。我们已经证明，海洋预测的极限是大约两个月。我们还表明，解决下降流与斜压不稳定以及对流沿着海洋锋是一个必要的成分，以模拟真实的次表层和中间条件在日本海。

The present basic research for developing ocean forecasting models has been conducted jointly by oceanographers of Tokyo Univ., Kyoto Univ., Kyushu Univ., Mie Univ., and Ehime Univ. with a particular Emphasis on the NEAR GOOS region. The major achievements are described in the following.We have developed an ultra high-resolution nested ocean model (with horizontal resolution of 1/18 degree) and have successfully simulated the vertical structure and the path of the Kuroshio. The model also resolves the ocean tide. Analyzing the model results, we have clarified the important role of JEBAR (joint effect of baroclinicity and bottom relief) in steering the Kuroshio eastward in the region southwest of the Kyushu Island ; the role of the bottom torque is to drive the Kuroshio into the deeper region. Tracer experiments show that about 50% (20%) of the water mass of the Tsushima Current is from the Taiwan Strait and another 50% (70%) is from the Kuroshio in summer (winter).The outflow of the Okhotsk Sea water of low potential vorticity is one of origins of the North Pacific Intermediate Water. Using a high-resolution non-hydrostatic ocean model, we have shown that eddy shedding due to the baroclinic instability of the front formed by tidal mixing plays a crucial role in this process. The water left from the Okhotsk Sea penetrates even into the Shikoku Basin.The RIAMMOM ocean model is successfully used for hindcasting experiments of currents in the Japan Sea. The data assimilation method used in the experimens is based on the Kalman filter. We have demonstrated that the ocean forecasting limit is about two months. We have also shown that to resolve downwelling associated with baroclinic instability as well as convection along the ocean front is a necessary ingredient to simulate realistical ly subsurface and intermediate conditions in the Japan Sea.