Evaluation of a Scalar Eddy Transport Coefficient Based on Geometric Constraints
Evaluation of a Scalar Eddy Transport Coefficient Based on Geometric Constraints
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DOI：
10.1016/j.ocemod.2016.12.004
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发表时间：
2017
期刊：
影响因子：
3.2
通讯作者：
S. Bachman;D. Marshall;J. Maddison;J. Mak
中科院分区：
文献类型：
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作者：
S. Bachman;D. Marshall;J. Maddison;J. Mak
一套理想化的模式是用来评估和比较几个先前提出的尺度的涡旋输送系数在下降梯度中尺度涡旋关闭。特别感兴趣的是，在这种比较是一个缩放介绍的一部分，涡参数化框架的马歇尔等人。（2012），其使用Eliassen-Palm涡动通量张量的固有几何导出。在下梯度闭合中使用该系数的主要优点是所有的量纲都被明确地指定，唯一的不确定性是一个无量纲参数α，它的大小以1为界。在每个模型中，一组被动示踪剂被初始化，其通量统计被用来反演涡致示踪剂输运。与以前的工作，这种技术已被用来诊断的线性通量梯度关系的张量系数，这些模型的理想化允许的横向涡输运被描述的标量系数。现存的缩放的技能，然后通过比较其预测值对使用这种方法诊断的系数进行测量。马歇尔等人（2012），缩放被示出为在所有模拟中与诊断的系数最接近地缩放。结果表明，这种缩放的技巧是由于它的功能依赖于总的涡动能量，这种缩放提供了一个很好的匹配诊断通量，即使在常数α的限制。可能的扩展这项工作，包括如何将所得的传输系数到根特和McWilliams参数化，进行了讨论。
A suite of idealized models is used to evaluate and compare several previously proposed scalings for the eddy transport coefficient in downgradient mesoscale eddy closures. Of special interest in this comparison is a scaling introduced as part of the eddy parameterization framework of Marshall et al. (2012), which is derived using the inherent geometry of the Eliassen–Palm eddy flux tensor. The primary advantage of using this coefficient in a downgradient closure is that all dimensional terms are explicitly specified and the only uncertainty is a nondimensional parameter,α, which is bounded by one in magnitude.In each model a set of passive tracers is initialized, whose flux statistics are used to invert for the eddy-induced tracer transport. Unlike previous work, where this technique has been employed to diagnose the tensor coefficient of a linear flux-gradient relationship, the idealization of these models allows the lateral eddy transport to be described by a scalar coefficient. The skill of the extant scalings is then measured by comparing their predicted values against the coefficients diagnosed using this method. The Marshall et al. (2012), scaling is shown to scale most closely with the diagnosed coefficients across all simulations. It is shown that the skill of this scaling is due to its functional dependence on the total eddy energy, and that this scaling provides an excellent match to the diagnosed fluxes even in the limit of constantα. Possible extensions to this work, including how to incorporate the resultant transport coefficient into the Gent and McWilliams parameterization, are discussed.