Theoretical and numerical study on shocks and subtropical front in a wind-driven oceanic gyre

风驱动海洋环流冲击和副热带锋的理论与数值研究

• 批准号: 07640567
• 负责人: KUBOKAWA Atsushi
• 金额: $ 1.41万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640567/
• 关键词: Ocean circulation; Subtropical countercurrent; Ocean general circulation model; Ventilated thermocline model; Subtropical front; Ventilated thermoclineモデル; 定在ロスビー波; 衝撃波

In the present study, the generation mechanism of the subtropical countercurrent and associated front is investigated by using an ocean general circulation model (GCM) with a simple geometry. A theory for the countercurrent is also presented.In the ocean GCM,the deep mixed layr occurs in the northern subtropical gyre and is shallows abruptly in the central subtropical gyre. The mixed-layr front, the narrow transition zone of the mixed-layr depth, slants from western central subtropical gyre to northeastern subtropical gyre, and the low potential vorticity fluid is produced at the intersection between the mixed-layr front and the outcrop line. Since the surface density is almost zonally uniform while the mixed-layr front slants northeastward, the minimum potential vorticity fluid in a dense isopycnal is produced in the northeastern region, while that in lighter density isopycnal in the western region. Subducted and advected southwestward, the low potential vorticity fluid in each isopycnal is vertically piled up and makes a thick low potential vorticity pool in the western central subtropical gyre. It is found that the model subtropical countercurrent occurs along the southwestern edge of this pool.Using a ventilated thermocline model, we investigate the effects of the mixed-layr depth distribution on the gyre structure, and it is demonstrated that the mechanism suggested by the numerical experiment can generate the countercurrent. On the other hand, southeastward slanting mixed-layr front can also generate a countercurrent. In the later case, a similar mechanism discussed by Dewar (1992) works. The characteristic equations suggest that the nonlinear steepening may also be important in this system.

在本研究中，使用简单的几何形状使用海洋通用循环模型（GCM）研究了亚热带逆流和相关前沿的生成机制。还提出了反流的理论。在海洋GCM中，深层混合层出现在北部亚热带的回旋中，并且在中央亚热带中突然呈浅。混合沿前线，混合层深度的狭窄过渡区，从西部中部亚热带陀螺到东北亚热带的斜侧，以及低潜在的涡流流体在混合layr前沿和露头线之间的交叉点产生。由于表面密度几乎是层次均匀的，而混合Layr前斜率向北向北，因此在东北地区产生密集的同相的最小电位涡度流体，而西部地区的较轻密度等值层。俯冲和向西向西南延伸，每种异配的低电位涡流都垂直堆积，并在中央中央亚热带中部的较厚的低电位涡度库中呈厚。发现模型亚热带反流沿该池的西南边缘发生。使用通风的热级模型，我们研究了混合-layr深度分布对GYRE结构的影响，并且证明了数值实验所建议的机制可以产生异流。另一方面，东南向倾斜的混合layr前部也可以产生反流。在后来的情况下，Dewar（1992）的工作讨论了类似的机制。特征方程式表明，非线性陡度在该系统中也可能很重要。

项目成果

久保川厚: "非線形ロスビー波と海洋循環構造" 京都大学数理解析研究所講究録(印刷中). (1997)

Atsushi Kubokawa：“非线性罗斯贝波和海洋环流结构”京都大学数学科学研究所Kokyuroku（出版中）。

久保川 厚: "非線形ロスビーと海洋循環構造" 京都大学数理解析研究所講究録. (印刷中). (1997)

Atsushi Kubokawa：“非线性罗斯贝和海洋环流结构”京都大学数学科学研究所 Kokyuroku（出版中）。

Kubokawa, A: "Nonlinear Rossby waves and structure of oceanic gyres (in Japanese)." Surikaiseki Kenkyujo Kokyuroku, Kyoto University. (in press). (1997)

Kubokawa，A：“非线性罗斯贝波和海洋环流结构（日语）。”