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首页> 外文期刊>Journal of Physical Oceanography >Loop Current Ring Shedding: The Formation of Cyclones and the Effect of Topography
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Loop Current Ring Shedding: The Formation of Cyclones and the Effect of Topography

机译：环流环脱落：旋风的形成和地形的影响

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The formation of cyclones in the vicinity of the Loop Current ring during the separation stage is analyzed in the frame of a high-resolution ECMWF daily wind-forced Miami Isopycnic Coordinate Ocean Model (MICOM) simulation. Mesoscale cyclones, observed in sea surface height maps in the vicinity of the Loop Current in a necking-down position, are found to contribute to the separation of the ring from the Loop Current as they grow between the Loop Current and the ring in the MICOM simulation. To understand the origin of the cyclones, the instability of the Loop Current idealized as an isolated vortex is studied. After noticing the cyclonic vorticity belt around the Loop Current, and based on the vertical distribution of potential vorticity in a Loop Current ring in the MICOM simulation, the linear stability of a shielded vortex is studied in the quasigeostrophic formalism. To simulate the effects of the planetary vorticity gradient and topography on the Loop Current, the nonlinear states of the idealized Loop Current are analyzed using the adiabatic MICOM code. Results from the analysis of the MICOM simulation show that cyclones are the products of a vortex rim instability. The modal analysis of the Loop Current instability reveals that mode 4 is the fastest-growing mode and that baroclinic (barotropic) instability is intensified in the deep (surface) layers. These results are confirmed by the analytical study of the idealized Loop Current. The nonlinear state shows that a Loop Current-like vortex is indeed a pentapole on an f plane. On the β plane, the northern cyclone is separated from the anticyclone by the β effect and both drift westward. When the topography of the Gulf of Mexico is taken into account—namely, the Campeche Bank, the southward slope north of the Loop Current, and the Florida shelf east of the Loop Current—several effects are observed: 1) the northern corner of the Campeche Bank erodes the Loop Current ring and its cyclones and interacts with the vortex's most unstable mode, 2) the northern southward slope scatters the northern cyclone while the anticyclone remains coherent and propagates to the west, and 3) realistic westward propagation speeds are obtained in the presence of the northern Campeche shelf, which acts as a mirror effect on the Loop Current ring, as opposed to the Florida shelf, which tends to block the ring.
机译：在高分辨率ECMWF日风强迫迈阿密等密度坐标海洋模型（MICOM）模拟的框架中，分析了分离阶段在环流环附近旋风的形成。在缩颈位置的环路电流附近海平面高度图中观察到的中尺度旋风，随着环流在MICOM中的环路电流和环之间的增长，有助于环与环路电流的分离。模拟。为了了解旋风分离器的起源，研究了理想化为隔离涡流的环路电流的不稳定性。在注意到环流附近的气旋涡流带之后，并根据MICOM模拟中环流环中势涡的垂直分布，在准地转形式学中研究了屏蔽涡的线性稳定性。为了模拟行星涡度梯度和地形对回路电流的影响，使用绝热MICOM代码分析了理想化回路电流的非线性状态。 MICOM模拟分析的结果表明，旋风分离器是涡旋边缘不稳定的产物。回路电流不稳定性的模态分析表明，模式4是增长最快的模式，并且深（表压）层的斜压（正压）不稳定性加剧。这些结果已通过对理想环路电流的分析研究得到证实。非线性状态表明，类似环路电流的涡流确实是f平面上的五极子。在β平面上，北部旋风通过β效应与反旋风分离，并且两者都向西漂移。当考虑到墨西哥湾的地形时，即坎佩切河岸，环路环流以北的南坡和环路环流以东的佛罗里达架，会观察到以下几种影响：1）墨西哥湾的北角坎佩切河岸侵蚀环流环及其旋风，并与涡旋最不稳定的模式相互作用； 2）北向南坡向北旋风散射，而反旋风保持连贯并向西传播，以及3）获得了现实的西向传播速度北部坎佩切（Campeche）大陆架的存在，在环流环上起到镜面作用，而佛罗里达大陆架则倾向于阻塞环。

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