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首页> 外文期刊>Journal of Physical Oceanography >Robustness of an Effective Diffusivity Diagnostic in Oceanic Flows
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Robustness of an Effective Diffusivity Diagnostic in Oceanic Flows

机译：在海洋流中进行有效扩散性诊断的鲁棒性

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摘要

The robustness of Nakamura's effective diffusivity diagnostic for quantifying eddy diffusivities of tracers within a stream wise-average framework is carefully examined in an oceanographic context, and the limits of its applicability are detailed. The near-surface Southern Ocean geostrophic flow, obtained from altimetric observations, is chosen for particular examination since it exhibits strong eddy activity. Careful analysis indicates that the effective diffusivity calculation is not strongly sensitive to the resolution of the velocity field or to the tracer initial conditions (after a spinup time of 3 months), and that a numerical diffusivity of 50 m~2 s~(-1) is appropriate to resolve the Batchclor scale at a computational resolution of 1/20°. The spatial variability of the effective diffusivity is examined and shown to be related to the eddy kinetic energy (EKE), mean zonal current (u), and phase speed of the eddies (c), following the streamwise averge of EKE/(u - c)~2, in agreement wilh linear baroclinic instability theory. The temporal variability of the effective diffusivity over the period 1996-2001 indicates significant variability on seasonal time scales with a magnitude of ±10% - 15%. Interannual variations are investigated and discussed in the context of changes in the wind stress associated with the southern annular mode.
机译：在海洋学背景下，仔细研究了Nakamura的有效扩散性诊断方法的稳健性，以量化示踪剂平均涡流在涡流中的涡流扩散性，并详细说明了其适用范围。从高空观测获得的近地表南洋地转流被选作特殊检查，因为它具有很强的涡流活动。仔细的分析表明，有效的扩散率计算对速度场的分辨率或示踪剂的初始条件（旋转时间为3个月后）不很敏感，数值扩散率为50 m〜2 s〜（-1） ）适用于以1/20°的计算分辨率解析Batchclor比例尺。根据EKE /（u-）的流平均，检查了有效扩散率的空间变异性，并显示出与涡动能（EKE），平均纬向电流（u）和涡流的相速度（c）有关。 c）〜2，符合线性斜压不稳定性理论。 1996年至2001年期间有效扩散率的时间变异性表明季节性时标具有明显的变异性，幅度为±10％-15％。在与南方环形模式相关的风应力变化的背景下，研究并讨论了年际变化。

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    《Journal of Physical Oceanography》 |2009年第9期|1993-2009|共17页
  • 作者

    Emily Shuckburgh; Helen Jones; John Marshall; Chris Hill;

  • 作者单位

    British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom;

    Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts;

    Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts;

    Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts;

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