Thermohaline layering on the microscale
Thermohaline layering on the microscale
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微尺度温盐分层
DOI：
10.1017/jfm.2018.976
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发表时间：
2019
影响因子：
3.7
通讯作者：
Radko, Timour
中科院分区：
文献类型：
--
作者：
Radko, Timour
建立了层结不稳定动力学的理论模型，这种不稳定常发生在指进对流活跃的海洋区域。温盐分层是由大规模分层和初级双扩散不稳定之间的相互作用驱动的，这些不稳定在微观尺度上运行--由分子耗散设定的时间和空间尺度。这种相互作用由直接数值模拟和渐近多尺度模式相结合来描述。多尺度理论被用来建立显式和动态一致的通量定律，该定律可以很容易地在大型分析和数值模式中实现。以往对温盐分层的理论研究大多基于通量梯度模型，该模型假定密度组分的垂直输运由其局部背景梯度唯一地决定。这种方法的主要缺点是，通量梯度模型预测的分层不稳定性在高波数时具有无界增长速率。由此产生的紫外线突变排除了对分层不稳定性的基本性质的分析，例如它的首选波长或最大生长速度。另一方面，多尺度模式包含了稳定短分层模式的超扩散项。总体而言，所提出的理论具有三重优势：(I)提供了对微观结构和分层模式之间相互作用的明确描述，(Ii)考虑了非均匀分层对微观结构驱动混合的影响，以及(Iii)避免了通量梯度定律在小尺度上的非物理行为。虽然这里以指进对流为例说明了时变小规模过程的多尺度参数化方法，但我们期望所提出的技术能够容易地适用于广泛的应用。
A theoretical model is developed which illustrates the dynamics of layering instability, frequently realized in ocean regions with active fingering convection. Thermohaline layering is driven by the interplay between large-scale stratification and primary double-diffusive instabilities operating at the microscale – temporal and spatial scales set by molecular dissipation. This interaction is described by a combination of direct numerical simulations and an asymptotic multiscale model. The multiscale theory is used to formulate explicit and dynamically consistent flux laws, which can be readily implemented in large-scale analytical and numerical models. Most previous theoretical investigations of thermohaline layering were based on the flux-gradient model, which assumes that the vertical transport of density components is uniquely determined by their local background gradients. The key deficiency of this approach is that layering instabilities predicted by the flux-gradient model have unbounded growth rates at high wavenumbers. The resulting ultraviolet catastrophe precludes the analysis of such basic properties of layering instability as its preferred wavelength or the maximal growth rate. The multiscale model, on the other hand, incorporates hyperdiffusion terms that stabilize short layering modes. Overall, the presented theory carries the triple advantage of (i) offering an explicit description of the interaction between microstructure and layering modes, (ii) taking into account the influence of non-uniform stratification on microstructure-driven mixing, and (iii) avoiding unphysical behaviour of the flux-gradient laws at small scales. While the multiscale approach to the parametrization of time-dependent small-scale processes is illustrated here on the example of fingering convection, we expect the proposed technique to be readily adaptable to a wide range of applications.
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影响因子：
4.6
作者：
W. Park
通讯作者：
W. Park
影响因子：
3.7
作者：
T. Radko
通讯作者：
T. Radko
DOI：
10.1016/0011-7471(69)90038-2
发表时间：
1969-11
期刊：
Deep Sea Research and Oceanographic Abstracts
影响因子：
--
作者：
M. Stern;J. S. Turner
通讯作者：
M. Stern;J. S. Turner
DOI：
--
发表时间：
2007
期刊：
影响因子：
--
作者：
Rachael D. Mueller;W. Smyth;B. Ruddick
通讯作者：
B. Ruddick
地带性不稳定
DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
K. Srinivasan;W. Young
通讯作者：
W. Young