The Evolution and Arrest of a Turbulent Stratified Oceanic Bottom Boundary Layer over a Slope: Upslope Regime and PV Dynamics
The Evolution and Arrest of a Turbulent Stratified Oceanic Bottom Boundary Layer over a Slope: Upslope Regime and PV Dynamics
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斜坡上湍流层状洋底边界层的演化和停止：上坡状态和光伏动力学
DOI：
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发表时间：
2021
影响因子：
3.5
通讯作者：
John R. Taylor
中科院分区：
文献类型：
--
作者：
X. Ruan;A. Thompson;John R. Taylor
本文探讨了在平均流存在下，倾斜海底和层结对海底边界层（BBL）演变的影响。作为对Ruan等人早期研究（https：//doi.org/10.1175/JPO-D-18-0079.1）的补充，该研究考察了下坡状态下的Ekman停滞，本文描述了上坡状态下Ekman停滞期间的湍流和BBL动力学。在上坡制度，加强层结发展响应上坡埃克曼运输和抑制湍流。使用一套大涡模拟，我们表明，BBL的演变可以描述在一个自相似的框架的基础上的无量纲数X/Xa。这个无量纲数被定义为密度表面的横向位移之间的比率在斜坡X和Ekman逮捕所需的位移Xa;后者可以从外部参数预测。此外，深度积分位涡的演变被认为是在上坡和下坡制度。PV破坏率在下坡政权被发现是生产率在上坡政权的两倍，使用相同的定义为底部混合层厚度。结果表明，这种不对称性与湍流应力活跃的深度尺度有关。这些结果是一个步骤，以改善参数化的BBL属性和演变的倾斜地形在粗分辨率的海洋模式。
The influence of a sloping bottom and stratification on the evolution of an oceanic bottom boundary layer (BBL) in the presence of a mean flow is explored. As a complement to an earlier study by Ruan et al. (https://doi.org/10.1175/JPO-D-18-0079.1) examining Ekman arrest in a downslope regime, this paper describes turbulence and BBL dynamics during Ekman arrest in the upslope regime. In the upslope regime, an enhanced stratification develops in response to the upslope Ekman transport and suppresses turbulence. Using a suite of large-eddy simulations, we show that the BBL evolution can be described in a self-similar framework based on a nondimensional number X/Xa. This nondimensional number is defined as the ratio between the lateral displacement of density surfaces across the slope X and a displacement Xa required for Ekman arrest; the latter can be predicted from external parameters. Additionally, the evolution of the depth-integrated potential vorticity is considered in both upslope and downslope regimes. The PV destruction rate in the downslope regime is found to be twice the production rate in the upslope regime, using the same definition for the bottom mixed layer thickness. It is shown that this asymmetry is associated with the depth scale over which turbulent stresses are active. These results are a step toward improving parameterizations of BBL properties and evolution over sloping topography in coarse-resolution ocean models.
影响因子：
3.5
作者：
L. Umlauf;W. Smyth;J. Moum
通讯作者：
L. Umlauf;W. Smyth;J. Moum
DOI：
10.1073/pnas.1904087116
发表时间：
2019-07-02
影响因子：
11.1
作者：
Garabato, Alberto C. Naveira;Frajka-Williams, Eleanor E.;Meredith, Michael P.
通讯作者：
Meredith, Michael P.