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

海洋环流小扰动引起的热量和盐度输送的数值研究

基本信息

批准号：
18540436
负责人：
HIRABARA Mikitoshi
金额：
$ 2.49万
依托单位：
Japan, Meteorological Research Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540436/
关键词：
Ocean general circulation model Small scale disturbances Diffusivity parameterization

项目摘要

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.

比较涡分辨模型（网格尺寸<10km；R网格）和涡允许模型（20km；P网格）的结果，以了解R网格模型比P模型能够更好地模拟海洋气候的原因-网格。使用湍流扩散方案的框架开发了子网格传输的参数化。将参数化应用于 P 网格模型并进行验证。副热带模式水和副热带逆流在 R 网格北太平洋模型 (NPERM5) 中得到真实模拟，而在 P 网格模型 (NPERM15) 中模拟效果不佳.NPERM5 比 NPERM15 能更好地体现中间盐度最小值，因为冷的新鲜 Oyashio 水和温热的黑潮盐水混合被大量的丝状物质强烈激活。 R 网格模型中的小横纹扰动在 Oyashio-Kuroshio 混合水区估算了涡流引起的厚度扩散系数和等密度扩散系数。 P 网格模型中系数的大小通常小于 R 网格模型中的系数的大小。 R网格模型中的等重系数大于厚度，因此，P网格模型无法模拟盐度最小值的主要原因是其等重混合非常弱。将R网格处的变量分解为空间平均值以及 P 网格上的异常，可以计算 P 网格的子网格传输（SGT）。制定了与密度水平SGT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子网格热量和盐度的传输。 P 网格模型中实现的参数化激活了等密度混合并改善了结果。