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首页> 外文期刊>Journal of Physical Oceanography >The Role of Horizontal Divergence in Submesoscale Frontogenesis
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The Role of Horizontal Divergence in Submesoscale Frontogenesis

机译：水平分歧在碱尺度前生的作用

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Oceanic surface submesoscale currents are characterized by anisotropic fronts and filaments with widths from 100 m to a few kilometers; an O(1) Rossby number; and large magnitudes of lateral buoyancy and velocity gradients, cyclonic vorticity, and convergence. We derive an asymptotic model of submeoscale frontogenesis-the rate of sharpening of submesoscale gradients-and show that in contrast with "classical" deformation frontogenesis, the near-surface convergent motions, which are associated with the ageostrophic secondary circulation, determine the gradient sharpening rates. Analytical solutions for the inviscid Lagrangian evolution of the gradient fields in the proposed asymptotic regime are provided, and emphasize the importance of ageostrophic motions in governing frontal evolution. These analytical solutions are further used to derive a scaling relation for the vertical buoyancy fluxes that accompany the gradient sharpening process. Realistic numerical simulations and drifter observations in the northern Gulf of Mexico during winter confirm the applicability of the asymptotic model to strong frontogenesis. Careful analysis of the numerical simulations and field measurements demonstrates that a subtle balance between boundary layer turbulence, pressure, and Coriolis effects (e.g., turbulent thermal wind; Gula et al. 2014) leads to the generation of the surface convergent motions that drive frontogenesis in this region. Because the asymptotic model makes no assumptions about the physical mechanisms that initiate the convergent frontogenetic motions, it is generic for submesoscale frontogenesis of O(1) Rossby number flows.
机译：海洋表面上尺度电流的特点是各向异性前方和长丝，宽度从100米到几千米; o（1）rossby编号;和横向浮力和速度梯度，旋风涡度和收敛性大的大小。我们得出了潜水血压前生的渐近模型 - 饲料升高的速度梯度 - 并表明与“经典”变形前源发生形成鲜明对比，近表面收敛运动与嗜型渐近的二次循环相关，确定梯度锐化率。提供了拟议的渐近政权中梯度领域的梯度领域的IncIscid Lagrangian演变的分析解决方案，并强调了核心运动在额相进化中的重要性。这些分析解决方案进一步用于导出伴随梯度锐化过程的垂直浮力通量的缩放关系。冬季墨西哥湾北部的现实数值模拟和漂移观测证实了渐近模型对强脑发生的适用性。对数值模拟和现场测量的仔细分析表明，边界层湍流，压力和科里奥利效应之间的微妙平衡（例如，湍流热风; Gula等，2014）导致产生促进前型内部的表面趋同运动这个地区。因为渐近模型没有关于发起会聚脑膜动作的物理机制的假设，所以它是o（1）rossby数流量的底层载体前大学的通用。

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