Diagnosing the Thickness‐Weighted Averaged Eddy‐Mean Flow Interaction From an Eddying North Atlantic Ensemble: The Eliassen‐Palm Flux
Diagnosing the Thickness‐Weighted Averaged Eddy‐Mean Flow Interaction From an Eddying North Atlantic Ensemble: The Eliassen‐Palm Flux
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DOI：
10.1029/2021ms002866
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发表时间：
2022-03
影响因子：
6.8
通讯作者：
T. Uchida;Q. Jamet;W. Dewar;J. Le Sommer;T. Penduff;D. Balwada
中科院分区：
文献类型：
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作者：
T. Uchida;Q. Jamet;W. Dewar;J. Le Sommer;T. Penduff;D. Balwada
厚度加权平均（TWA）框架将剩余平均流量视为预测变量，提供了对剩余平均流量的涡流反馈的明确理论公式。TWA框架中涉及的平均算子，尽管在理论上是集合平均，但在实践中经常近似于时间平均。在这里，我们在中尺度允许的分辨率（1/12°）下分析了北大西洋模拟的集合。因此，我们根据系综平均值和关于这些平均值的波动来识别平均值和涡旋。系综维度与时间和空间维度正交，否定了在定义涡流时对任意时间或空间尺度的必要性。涡均流反馈被封装在Eliassen-Palm（E-P）通量张量中，其收敛表明涡动量通量在分离的墨西哥湾流中占主导地位。涡旋可以解释为有助于墨西哥湾流的纬向弯曲和它在纬向北迁移。在北大西洋海流区分离湾流下游，界面形式的应力辐合成为E-P通量辐合的主导阶次。
The thickness‐weighted average (TWA) framework, which treats the residual‐mean flow as the prognostic variable, provides a clear theoretical formulation of the eddy feedback onto the residual‐mean flow. The averaging operator involved in the TWA framework, although in theory being an ensemble mean, in practice has often been approximated by a temporal mean. Here, we analyze an ensemble of North Atlantic simulations at mesoscale‐permitting resolution (1/12°). We therefore recognize means and eddies in terms of ensemble means and fluctuations about those means. The ensemble dimension being orthogonal to the temporal and spatial dimensions negates the necessity for an arbitrary temporal or spatial scale in defining the eddies. Eddy‐mean flow feedbacks are encapsulated in the Eliassen‐Palm (E‐P) flux tensor and its convergence indicates that eddy momentum fluxes dominate in the separated Gulf Stream. The eddies can be interpreted to contribute to the zonal meandering of the Gulf Stream and a northward migration of it in the meridional direction. Downstream of the separated Gulf Stream in the North Atlantic Current region, the interfacial form stress convergence becomes leading order in the E‐P flux convergence.