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首页> 外文期刊>Journal of Physical Oceanography >Curved Density Fronts: Cyclogeostrophic Adjustment and Frontogenesis
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Curved Density Fronts: Cyclogeostrophic Adjustment and Frontogenesis

机译：弯曲的密度前沿：旋流调整和锋生

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摘要

Curvature can play a significant role in the dynamics of density fronts at small scales and in low-latitude regions of the ocean. Fronts can be displaced from balance by rapid forcing and undergo an adjustment toward a more stable state or be strained and sharpened by surrounding flow in a process known as frontogenesis. This study investigates the role of curvature in adjustment and frontogenesis using the idealized configuration of an axisymmetric eddy and associated circular front. As a result of the curvature, the balanced state of this system is not geostrophic balance, where pressure and Coriolis forces exactly balance, but cyclogeostrophic balance, where pressure and Coriolis forces combine to supply a net inwards centripetal force on fluid parcels. The parameter range for which cyclogeostrophically balanced states exist for a given unbalanced initial condition is determined. This parameter range is smaller for anticyclonic fronts (i.e., fronts curved around a warm core), which have larger angular velocities than comparable straight fronts, implying they are more likely to break down during adjustment. The reverse is true for cyclonic fronts. A model for the sharpening of a curved front in a background strain flow, analogous to the Hoskins and Bretherton (1972) model for a straight front, is developed. Relative to a straight front subject to the same strain rate, vertical velocities are weaker for an anticyclonic front and stronger for a cyclonic front. Anticyclonic fronts collapse to a near discontinuity during frontogenesis far more rapidly than cyclonic fronts for the same strain rate.
机译：曲率在小规模和低纬度海洋区域的密度锋面动力学中可以发挥重要作用。可以通过快速施力使锋线脱离平衡，并朝更稳定的状态进行调整，或者在称为前生的过程中因周围的流动而使锋线变尖锐。这项研究使用轴对称涡流和相关的圆形前沿的理想配置，研究了曲率在调节和前生中的作用。由于曲率，该系统的平衡状态不是地转平衡（压力和科里奥利力精确平衡），而是环地转平衡（压力和科里奥利力相结合以在流体包裹上提供净的向内向心力）。确定给定的不平衡初始条件下存在地地平衡状态的参数范围。对于反旋风锋面（即，围绕暖芯弯曲的锋面），此参数范围较小，与可比较的笔锋锋利相比，其角速度更大，这意味着它们在调整过程中更容易破裂。对于气旋锋面则相反。与Hoskins and Bretherton（1972）的笔直笔直模型相似，开发了一种用于在背景应变流中锐化笔尖的模型。相对于承受相同应变率的笔直锋面，垂直速度对于反气旋锋面较弱，而对于气旋锋面则较快。在相同的应变速率下，反气旋锋面在锋生过程中崩溃到几乎不连续，远比气旋锋面快。

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  • 来源
    《Journal of Physical Oceanography》 |2016年第10期|3193-3207|共15页
  • 作者

    Shakespeare Callum J.;

  • 作者单位

    Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT, Australia|Australian Natl Univ, ARC Ctr Excellence Climate Syst Sci, Canberra, ACT, Australia;

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  • 正文语种 eng
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