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

目前发展海洋预报模式的基础研究是由东京大学、京都大学、九州大学、三重大学和爱媛大学的海洋学家联合进行的，特别强调近GOOS区域。主要成果如下。我们开发了超高分辨率嵌套海洋模型（水平分辨率为1/18度），并成功模拟了黑潮的垂直结构和路径。该模型还可以解析海潮。通过对模型结果的分析，明确了JEBAR（斜压性和底起伏的联合效应）在九州岛西南地区引导黑潮东移的重要作用；底部扭矩的作用是驱动黑潮进入更深的区域。示踪实验表明，对马流夏季（冬季）约50%（20%）的水团来自台湾海峡，另外50%（70%）的水团来自黑潮。鄂霍次克海低位涡的流出是北太平洋中水的源头之一。利用高分辨率的非流体静力海洋模型，我们已经表明，由于潮汐混合形成的锋面斜压不稳定而导致的涡流脱落在这一过程中起着至关重要的作用。鄂霍次克海留下的水甚至渗透到四国盆地。RIAMMOM海洋模式成功地应用于日本海海流的后播试验。实验中使用的数据同化方法是基于卡尔曼滤波的。我们已经证明，海洋预报的极限大约是两个月。我们还表明，解决与斜压不稳定以及沿海锋的对流相关的下降是模拟日本海真实的地下和中间条件的必要因素。

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.