High-resolution modelling of a large-scale river plume
High-resolution modelling of a large-scale river plume
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DOI：
10.1007/s10236-013-0653-x
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发表时间：
2013-10
期刊：
影响因子：
2.3
通讯作者：
V. Vlasenko;N. Stashchuk;R. Mcewan
中科院分区：
文献类型：
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作者：
V. Vlasenko;N. Stashchuk;R. Mcewan
利用马萨诸塞州理工学院的大气环流模式对大尺度河流羽流的演变进行了数值研究。模型参数的设置接近于在哥伦比亚河口地区观察到的参数。精细分辨率网格沿着与非流体静力学分散包括在模型中允许复制详细的内部羽流结构，以及从羽流的边界辐射的内波系统。有人发现，不仅第一模式，而且第二和第三模式的内波辐射从羽在其松弛的最后阶段时，前传播的速度下降到低于一个适当的波相速度的内部斜压模式。模型输出表明，这些高模式波的振幅是相同的顺序作为领先的第一模式波，这在特定的垂直结构（最大结构功能的位置超出密度跃层）相结合，创造了有利的条件，剪切不稳定性的产生。高分辨率模型输出还揭示了羽流精细内部结构的证据，其特征是羽流内部存在次级锋，次级内波系统从升空区域向外边界径向传播。这些结构加强了传播羽流内的混合过程，在羽流主体和下沃茨之间的下边界上发展的卷吸机制占优势。通过在口部附近不同深度释放的拉格朗日漂流物的方法再现了烟羽中的水平环流方案。
Evolution of a large-scale river plume is studied numerically using the Massachusetts Institute of Technology general circulation model. The model parameters were set close to those observed in the area of the Columbia River mouth. The fine-resolution grid along with the non-hydrostatic dispersion included in the model allowed for the reproduction of detailed inner plume structure, as well as a system of internal waves radiated from the plume’s boundary. It was found that not only first-mode but also second- and third-mode internal waves are radiated from the plume at the latest stages of its relaxation when the velocity of the front propagation drops below an appropriate wave phase speed of internal baroclinic mode. The model output shows that the amplitude of these high-mode waves is of the same order as the leading first-mode waves, which in combination with the specific vertical structure (location of the maximum structure function beyond the pycnocline layer) creates favourable conditions for the generation of shear instabilities. High-resolution model output also reveals evidence of a fine internal structure of the plume characterized by the presence of secondary fronts inside the plume and secondary internal wave systems propagated radially from the lift-off area to the outer boundary. These structures intensify the mixing processes within the propagating plume with predominance of the entrainment mechanism developing on the lower boundary between the plume’s body and underlying waters. The scheme of horizontal circulation in the plume was reproduced by the methodology of Lagrange drifters released near the mouth at different depths.