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首页> 外文期刊>Journal of Physical Oceanography >A Diagnosis of Thickness Fluxes in an Eddy-Resolving Model
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A Diagnosis of Thickness Fluxes in an Eddy-Resolving Model

机译：涡旋解析模型中厚度通量的诊断

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Output from an eddy-resolving model of the North Atlantic Ocean is used to estimate values for the thickness diffusivity κ appropriate to the Gent and McWilliams parameterization. The effect of different choices of rotational eddy fluxes on the estimated κ is discussed. Using the raw fluxes (no rotational flux removed), large negative values (exceeding -5000 m~2 s~(-1)) of κ are diagnosed locally, particularly in the Gulf Stream region and in the equatorial Atlantic. Removing a rotational flux based either on the suggestion of Marshall and Shutts or the more general theory of Medvedev and Greatbatch leads to a reduction of the negative values, but they are still present. The regions where κ < 0 correspond to regions where eddies are acting to increase, rather than decrease (as in baroclinic instability) the mean available potential energy. In the subtropical gyre, κ ranges between 500 and 2000 m~2 s~(-1), rapidly decreasing to zero below the thermocline in all cases. Rotational fluxes and κ are also estimated using an optimization technique. In this case, |κ| can be reduced or increased by construction, but the regions where κ < 0 are still present and the optimized rotational fluxes also remain similar to a priori values given by the theoretical considerations. A previously neglected component (v) of the bolus velocity is associated with the horizontal flux of buoyancy along, rather than across, the mean buoyancy contours. The v component of the bolus velocity is interpreted as a streamfunction for eddy-induced advection, rather than diffusion, of mean isopycnal layer thickness, showing up when the lateral eddy fluxes cannot be described by isotropic diffusion only. All estimates show a similar large-scale pattern for v, implying westward advection of isopycnal thickness over much of the subtropical gyre. Comparing v with a mean streamfunction shows that it is about 10% of the mean in midlatitudes and even larger than the mean in the Tropics.
机译：来自北大西洋的涡旋解析模型的输出用于估计适合Gent和McWilliams参数化的厚度扩散系数κ的值。讨论了不同选择的旋转涡流对估计κ的影响。使用原始磁通量（未去除旋转磁通量），局部诊断出较大的κ负值（超过-5000 m〜2 s〜（-1）），特别是在墨西哥湾流地区和赤道大西洋。根据Marshall和Shutts的建议或者更广义的Medvedev和Greatbatch理论删除旋转通量会导致负值减小，但它们仍然存在。 κ<0的区域对应于涡旋作用的区域，该区域的平均可用势能增加而不是减少（如斜压不稳定）。在亚热带回旋中，κ的范围在500至2000 m〜2 s〜（-1）之间，在所有情况下均在温跃层以下迅速减小至零。旋转通量和κ也是使用优化技术估算的。在这种情况下，|κ|通过构造可以减小或增加，但是κ＜0的区域仍然存在，并且优化的旋转通量也保持与理论考虑给出的先验值相似。推注速度的先前被忽略的分量（v）与沿着而不是穿过平均浮力轮廓线的水平浮力有关。推注速度的v分量被解释为涡流对流的流函数，而不是平均等深层厚度的扩散，当横向涡流不能仅通过各向同性扩散来描述时出现。所有估计值都显示出类似的v的大规模模式，这意味着在大部分亚热带回旋上等密度厚度向西平流。将v与平均流函数进行比较表明，它在中纬度约占平均值的10％，甚至大于热带地区的平均值。

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