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首页> 外文期刊>Journal of Physical Oceanography >Continental Shelf Baroclinic Instability. Part I: Relaxation from Upwelling or Downwelling
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Continental Shelf Baroclinic Instability. Part I: Relaxation from Upwelling or Downwelling

机译：大陆架斜斜不稳定。第一部分：上升流或下降流带来的放松

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There exists a good deal of indirect evidence, from several locations around the world, that there is a substantial eddy field over continental shelves. These eddies appear to have typical swirl velocities of a few centimeters per second and have horizontal scales of perhaps 5-10 km. These eddies are weak compared to typical, wind-driven, alongshore flows but often seem to dominate middepth cross-shelf flows. The idea that motivates the present contribution is that the alongshore wind stress ultimately energizes these eddies by means of baroclinic instabilities, even in cases where obvious intense fronts do not exist. The proposed sequence is that alongshore winds over a stratified ocean cause upwelling or downwelling, and the resulting horizontal density gradients are strong enough to fuel baroclinic instabilities of the requisite energy levels. This idea is explored here by means of a sequence of idealized primitive equation numerical model studies, each driven by a modest, nearly steady, alongshore wind stress applied for about 5-10 days. Different runs vary wind forcing, stratification, bottom slope, bottom friction, and Coriolis parameter. All runs, both upwelling and downwelling, are found to be baroclinically unstable and to have scales compatible with the underlying hypothesis. The model results, combined with physically based scalings, show that eddy kinetic energy generally increases with bottom slope, stratification, wind impulse (time integral of the wind stress), and inverse Coriolis parameter. The dominant length scale of the eddies is found to increase with increasing eddy kinetic energy and to decrease with Coriolis parameter.
机译：来自世界各地的大量间接证据表明，大陆架上有大量涡流场。这些涡流似乎具有每秒几厘米的典型旋流速度，并且可能具有5-10 km的水平尺度。与典型的风力驱动的近岸流相比，这些涡流较弱，但通常似乎在中深跨架流中占主导地位。激发当前贡献的想法是，即使在不存在明显的强烈锋线的情况下，沿海风应力最终也会通过斜压不稳定性使这些涡旋激发。提出的顺序是，分层海洋上的近海风引起上升或下降，并且所产生的水平密度梯度足够强到足以引起所需能量水平的斜压不稳定。这里通过一系列理想化的原始方程数值模型研究来探索这个想法，每个模型研究都由施加了大约5-10天的适度，近乎稳定的沿岸风应力驱动。不同的运行会改变风力，分层，底部坡度，底部摩擦力和科里奥利参数。发现所有上升流和下降流的行程都是斜压不稳定的，并且规模与基本假设兼容。模型结果与基于物理的缩放比例相结合，显示出涡动能通常随底坡度，分层，风冲量（风应力的时间积分）和反科里奥利参数而增加。发现涡流的主要长度尺度随涡流动能的增加而增加，而随科里奥利参数减小。

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