The role of secondary circulation in boundary mixing
The role of secondary circulation in boundary mixing
复制标题
二次循环在边界混合中的作用
DOI：
10.1029/jc095ic03p03181
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发表时间：
1990
影响因子：
--
通讯作者：
C. Garrett
中科院分区：
文献类型：
--
作者：
C. Garrett
倾斜边界附近的增强混合减少了分层，从而减少了垂直扩散浮力传输。然而，额外的平流浮力通量与边界附近的浮力驱动的双向二次流相关。一些积分关系和简单的物理论证表明，平流虽然增加了下坡浮力输送，但减少了垂直输送；边界混合的总体有效性涉及减少因子的平方，该减少因子在分层减少的区域中单独发生扩散通量。然而，二次循环可以通过恢复分层从而间接增加边界混合的有效性，从而恢复扩散通量，除非这种重新分层也抑制了混合。还导出了沿坡流的积分关系，该流是解的一部分而不是任意的，并且讨论了该理论与 Ekman 层动力学的关系。
Enhanced mixing near a sloping boundary reduces the stratification and hence the vertical diffusive buoyancy transport. An additional advective buoyancy flux, however, is associated with the bidirectional secondary flow driven by buoyancy forces near the boundary. Some integral relations and simple physical arguments show that, while advection increases the downslope buoyancy transport, it decreases the vertical transport; the overall effectiveness of boundary mixing involves the square of the reduction factor that would occur for the diffusive flux alone in a region of reduced stratification. The secondary circulation may increase the effectiveness of boundary mixing, indirectly, however, by restoring the stratification, and hence the diffusive fluxes, unless this restratification also suppresses the mixing. Integral relations are also derived for the along-slope flow which is part of the solution rather than arbitrary, and the relationship of the theory to Ekman layer dynamics is discussed.