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首页> 外文期刊>Journal of Physical Oceanography >Finite-Amplitude Evolution of Instabilities Associated with the Coastal Upwelling Front
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Finite-Amplitude Evolution of Instabilities Associated with the Coastal Upwelling Front

机译：与海岸上升流前沿相关的不稳定性的有限幅度演化

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A primitive equation model is used to study the finite-amplitude evolution of instabilities associated with the coastal upwelling front. Simulations of increasing complexity are examined that represent idealizations of summer conditions off the Oregon coast, including cases with steady and with time-variable wind in a domain with alongshore-uniform bathymetry and with time-variable wind in a domain with realistic Oregon coast bathymetry. The numerical results indicate that the fastest-growing mode in this system has approximately an 8-10-km alongshore wavelength but that, once the disturbances grow to finite amplitude, the predominant alongfront scale increases rapidly because of nonlinear effects. Separation of the total kinetic energy into contributions from the alongshore average flow and perturbation about that average shows that the initial growth of the perturbation kinetic energy is due to potential energy conversion, but transfer of energy from the kinetic energy of the alongshore average flow becomes important once the disturbances reach large amplitude. The time-variable wind simulations again show initial growth of small-scale instabilities followed by evolution to larger scales. In this case, however, even after larger-scale disturbances have developed on the upwelling front, smaller-scale patterns amplify along the front in response to each upwelling-favorable wind event. Realistic coastal bathymetry introduces additional alongshore topographic scales into the problem, but the formation of instabilities on small scales and evolution to larger scales are still ubiquitous. Where instabilities encounter strong curvature in the upwelling front produced by bathymetric effects, the upwelling front becomes highly contorted and horizontal variability is significantly enhanced.
机译：使用原始方程模型研究与海岸上升流前沿相关的不稳定性的有限幅度演化。考察了日益增加的复杂性模拟，这些模拟代表了俄勒冈州沿海夏季条件的理想化，包括沿岸均匀测深的地区具有稳定且随时间变化的风的情况以及具有实际俄勒冈海岸的测深与时变风的情况。数值结果表明，该系统中增长最快的模式沿岸波长约为8-10 km，但一旦扰动增长到有限幅度，由于非线性效应，主要的沿前尺度迅速增加。将总动能分解为沿岸平均流量的贡献并以该平均值为中心进行扰动，表明扰动动能的初始增长是由于势能转换引起的，但是从沿岸平均流的动能转移能量变得很重要一旦干扰达到大幅度。随时间变化的风模拟再次显示出小规模不稳定性的初始增长，然后演变为更大规模。然而，在这种情况下，即使在上升流前沿发生了较大规模的扰动之后，响应于每个上升流有利的风事件，较小尺度的模式仍沿前沿放大。现实的沿海测深法将更多的沿海地形尺度引入了该问题，但是小尺度的不稳定性的形成以及向更大尺度的演化仍然无处不在。在不稳定性遇到由测深效应产生的上升流锋中的强烈曲率的情况下，上升流锋变得高度扭曲，并且水平变化性显着增强。

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