Numerical study about heat and salinity transports induced by small disturbances in an ocean general circulation

对比了涡旋解析模式（栅格尺寸<10km； r -栅格）和涡旋允许模式（20km； p -栅格）的模拟结果，了解了r -栅格模式比p -栅格模式能更好地模拟海洋气候学的原因。利用湍流扩散格式的框架，建立了子网格输运的参数化方法。对p网格模型进行了参数化，并进行了验证。北太平洋r格网模式（NPERM5）对副热带模态水和副热带逆流的模拟较为真实，而p格网模式（NPERM15）对副热带模态水和副热带逆流的模拟较差。与NPERM15相比，NPERM5能更好地代表中间盐度最小值，这是由于在r -网格模型中，大量丝状小波扰动激活了冷淡水和温咸水混合。p网格模型的系数大小一般小于r网格模型。因此，p格网模型不能模拟盐度最小值的主要原因是其等压混合作用非常弱。将r网格上的变量分解为p网格上的空间平均值及其异常，可以计算p网格上的子网格输运（SGT）。建立了与密度水平梯度相一致的三维反对称混合张量。通过该张量对应的扩散通量可以实现亚网格热盐输运。在p网格模型中实现的参数化激活了等尺度混合，改善了结果。

Results from an eddy-resolving model (grid-size<10km; R-grid) and an eddy-permitting model (20km; P-grid) were compared to understand the reason why R-grid model can simulate the ocean climatology better than P-grid. A parameterization of sub-grid transport was developed using the framework of turbulent diffusion scheme. The parameterization was implemented to a P-grid model and validated.The subtropical mode water and the subtropical countercurrent are realistically simulated in a R-grid North Pacific model (NPERM5), while they are poorly simulated in a P-grid model (NPERM15).The intermediate salinity minimum can be better represented in NPERM5 than in NPERM15, because cold fresh Oyashio water and warm saline Kuroshio water mix vigorously activated by numbers of filament-like small-wale disturbances in the R-grid model The eddy-induced thickness diffusivity and the isopycnal diffusivity coefficients were estimated in the Oyashio-Kuroshio mixed water region. The magnitudes of the coefficients are generally smaller in P-grid model than R-grid. The isopycnal coefficient is larger than thickness in the R-grid model Therefore, the primary reason why the salinity minimum cannot be simulated in P-grid model is the very weak isopycnal mixing in it.Decomposing the variables at R-grids into the spatial average and the anomalies from it over a P-grid, the sub-grid transport (SGT) fir the P-grid can be calculated. The three-dimensional anti-symmetric mixing tensor consistent with the horizontal SGT of density was formulated. The sub-grid heat and salinity transport can be realized through the diffusive flux corresponding to this tensor. The parameterization implemented in a P-grid model activates the isopycnal mixing and improves the result.