The evolution of a front in turbulent thermal wind balance. Part 1. Theory
The evolution of a front in turbulent thermal wind balance. Part 1. Theory
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湍流热风平衡锋面的演变。
DOI：
10.1017/jfm.2018.448
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发表时间：
2018
影响因子：
3.7
通讯作者：
John R. Taylor
中科院分区：
文献类型：
--
作者：
M. Crowe;John R. Taylor
在这里，我们研究小尺度湍流的海洋和大气中的锋的演变的影响。具体而言，我们认为一个初始平衡的密度前的演变受到施加的粘性和扩散作为一个简单的模拟小尺度湍流。在晚些时候，占主导地位的平衡被发现是准定常湍流热成风平衡与时间演变由于对流扩散平衡的浮力方程。我们使用的领先的顺序平衡，以确定分析相似的解决方案的扩展前，并发现扩展速率是最大的中间值的埃克曼数，与扩展导致剪切分散与横向前流和垂直扩散的密度。在响应剪切分散，前面的密度分布，这是近线性的交叉前坐标演变。在锋区的边缘，密度场发展出大曲率，这些区域与强烈垂直速度的窄带相关联。
Here, we examine the influence of small-scale turbulence on the evolution of fronts in the ocean and atmosphere. Specifically, we consider the evolution of an initially balanced density front subject to an imposed viscosity and diffusivity as a simple analogue for small-scale turbulence. At late times, the dominant balance is found to be the quasisteady turbulent thermal wind balance with time evolution due to an advection–diffusion balance in the buoyancy equation. We use the leading-order balance to determine analytical similarity solutions for the spreading of a front and find that the spreading rate is maximum for an intermediate value of the Ekman number, with the spreading resulting from shear dispersion associated with the cross-front flow and vertical diffusion of density. In response to shear dispersion, the front evolves towards a density profile that is nearly linear in the cross-front coordinate. At the edges of the frontal zone, the density field develops large curvature, and these regions are associated with narrow bands of intense vertical velocity.