Meridional Location and Profile of a Prematurely Separated WBC Extension Jet in a Two-Layer System
Meridional Location and Profile of a Prematurely Separated WBC Extension Jet in a Two-Layer System
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DOI：
10.1175/jpo-d-21-0313.1
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发表时间：
2023-04-01
影响因子：
3.5
通讯作者：
Kubokawa, Tsushi
中科院分区：
文献类型：
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作者：
Kubokawa, Tsushi
无滑移边界条件下的西边界流（WBCs）倾向于从海岸分离前（没有达到intergyre边界），并形成向东的急流。本研究使用一个两层准地转模式，从理论上考虑了一个过早分离的WBC延伸急流的纬向结构和位置。在急流两侧和急流下方均为均匀化位涡区的条件下，建立了一个西副热带环流纬向廓线的简单模式。本文阐明，如果除了Sverdrup纬向流的纬向廓线和垂直层结外，还能给出两个变量，如PV锋面的强度（穿过急流的PV差）和急流中心的流函数值，就能确定纬向结构。两层的纬向速度剖面与数值试验结果吻合较好。当喷流接近涡间边界时，喷流的纬向位置仅取决于锋面的强度。当北方环流与环流间边界分离且局地风对急流的影响可以忽略时，与数值试验结果的比较表明，急流的中心流线与向东的Sverdrup流的中心流线相连接。我们还发现，向下的埃克曼泵送速度的射流向南移动。
Western boundary currents (WBCs) under no-slip boundary conditions tend to separate from the coast pre-maturely (without reaching the intergyre boundary) and form eastward jets. This study theoretically considers the meridional structure and location of a prematurely separated WBC extension jet using a two-layer quasigeostrophic model. Assuming homogenized potential vorticity (PV) regions on both sides of and below the jet, we constructed a simple model for the meridional profiles of the zonal flows in the western subtropical gyre. This work clarifies that the meridional structure can be determined if two variables, such as the strength of the PV front (difference in PV across the jet) and the value of the stream -function at the jet's center, are given in addition to the meridional profile of the Sverdrup zonal flow and the vertical stratifica-tion. The zonal velocity profiles in both layers agreed well with those obtained by numerical experiments. When the jet is close to the intergyre boundary, the meridional location of the jet depends only on the front's strength. When the northern re-circulation gyre is detached from the intergyre boundary and the local wind effect on the jet is negligible, comparisons with the numerical experiments suggest that the jet's central streamline connects to the central streamline of the eastward Sverdrup flow. We also found that a downward Ekman pumping velocity shifts the jet southward.