A Multiwavenumber Theory for Eddy Diffusivities and Its Application to the Southeast Pacific (DIMES) Region
A Multiwavenumber Theory for Eddy Diffusivities and Its Application to the Southeast Pacific (DIMES) Region
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DOI：
10.1175/jpo-d-14-0229.1
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发表时间：
2015-07-01
影响因子：
3.5
通讯作者：
Griesel, Alexa
中科院分区：
文献类型：
--
作者：
Chen, Ru;Gille, Sarah T.;Griesel, Alexa
用多波数理论表示涡流扩散系数。它扩展了早期的单波数理论，并包括涡流运动中包含的波数的广泛范围。在海洋涡旋仅由单个波数组成的极限情况下，多波数理论与单波数理论等效，均表现出涡旋传播相对于平均流的混合抑制作用。多波数理论在南大洋的一个区域（南纬70度-45度，西经110度-20度）进行了测试，该区域覆盖了德雷克海峡，包括在南大洋的深环流和等环流混合实验（DIMES）期间的示踪剂/漂浮物释放地点。通过单波数理论、多波数理论和全球1/10度平行海洋计划（POP）模拟中部署的浮子，估算了该区域的横流涡旋扩散系数和混合长度。与单波数理论相比，多波数理论的横流混合长度的水平结构在几乎所有深度水平上都与基于模拟浮子的估计更吻合。多波数理论较好地反映了南极环极流内外跨流混合长度的垂直结构。单波数理论和多波数理论都表示横流扩散系数的水平结构，类似于涡流动能模式。
A multiwavenumber theory is formulated to represent eddy diffusivities. It expands on earlier single-wavenumber theories and includes the wide range of wavenumbers encompassed in eddy motions. In the limiting case in which ocean eddies are only composed of a single wavenumber, the multiwavenumber theory is equivalent to the single-wavenumber theory and both show mixing suppression by the eddy propagation relative to the mean flow. The multiwavenumber theory was tested in a region of the Southern Ocean (70 degrees-45 degrees S, 110 degrees-20 degrees W) that covers the Drake Passage and includes the tracer/float release locations during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). Cross-stream eddy diffusivities and mixing lengths were estimated in this region from the single-wavenumber theory, from the multiwavenumber theory, and from floats deployed in a global 1/10 degrees Parallel Ocean Program (POP) simulation. Compared to the single-wavenumber theory, the horizontal structures of cross-stream mixing lengths from the multiwavenumber theory agree better with the simulated float-based estimates at almost all depth levels. The multiwavenumber theory better represents the vertical structure of cross-stream mixing lengths both inside and outside the Antarctica Circumpolar Current (ACC). Both the single-wavenumber and multiwavenumber theories represent the horizontal structures of cross-stream diffusivities, which resemble the eddy kinetic energy patterns.