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首页> 外文期刊>Journal of Marine Research >Buoyant discharge on the inner continental shelf: A frontal model
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Buoyant discharge on the inner continental shelf: A frontal model

机译：内陆大陆架上的浮力排放：正面模型

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摘要

A steady state, frontal model of the arrested topographic wave type (Csanady, 1978) is developed for application to buoyant coastal discharge of large-scale and weak stratification, typically found on the inner continental shelf. The across-shore momentum balance is geostrophic, while the alongshore momentum balance includes wind stress and bottom or interfacial friction. The dynamics thus has semi-geostrophic character. No mixing dynamics is present. The model has two major purposes: first, to serve as the vehicle for a process study requiring only moderate computing resources, and second, to inquire into the general consequences of extending the original single-layer model of Csanady (1978) into a two-layer, frontal model for application to buoyant coastal discharge. Analysis of the flow near the frontal bottom intersection shows that the bottom stresses on each side of the front must be equal and match as well the interfacial stress just above. Similar analysis near the surface front shows that static stability there requires the presence of only downwelling-favorable wind stress. This implies that a statically stable, steady state is not possible for upwelling-favorable winds. The model possesses an asymptotic downshelf state that is termed frictionally adjusted flow in which alongshore gradients and across-shore velocities vanish and bottom, interfacial, and wind stresses all are equal. The front then becomes trapped to the local isobaths. Numerical experiments showed that the model contains possible spatially growing instability because of the frontal boundary. Weaker baroclinic strength and diminished bottom slopes tended to increase flow stability. Stable flows were computed in their evolution from a prescribed upshelf state intended to simulate estuarine outflow of buoyant discharge and adjacent inflow of denser ambient shelf water. A turning region developed where the front moved first offshore then back nearer the coast. Experiments showed that the turning region was a joint product of the turning isobath geometry imposed near the estuary mouth and the estuarine inflow of shelf water. Comparisons of model results with recent observations of the Delaware Coastal Current showed general qualitative agreement, but highlight the lack of model mixing processes.
机译：建立了一种稳定的地形波类型的前沿模型（Csanady，1978），用于大面积薄弱分层的沿海浮力排水，通常在大陆架内部。岸上动量平衡是地转的，而岸上动量平衡包括风应力和底部或界面摩擦。因此，动力学具有半地转特征。没有混合动力。该模型有两个主要目的：一是充当仅需要适度计算资源的过程研究的载体，二是研究将Csanady（1978）的原始单层模型扩展为两个模型的一般结果：层，用于浮力沿海排放的额叶模型。对前部底部相交处附近流动的分析表明，前部各侧的底部应力必须相等且与上面的界面应力匹配。在地表前缘附近进行的类似分析表明，那里的静态稳定性只需要存在下压有利的风应力。这意味着对于上升气流有利的风不可能达到静态稳定的状态。该模型具有渐近的下架状态，该状态称为摩擦调整流，其中沿岸的梯度和跨岸的速度消失，且底部，界面和风应力均相等。然后，前部被困在局部等值线中。数值实验表明，该模型包含可能由于正面边界而在空间上增长的不稳定性。斜压强度减弱和底部斜率减小往往会增加流动稳定性。从规定的上架状态计算出稳定的流量，以模拟河口浮力排放和邻近的较稠密环境水的流入。形成了一个转弯区域，前部首先移动到海上，然后又返回到更靠近海岸的区域。实验表明，转弯区域是河口附近施加的转弯等压线几何形状和架子水入河口的联合产物。将模型结果与最近对特拉华沿海海流的观测结果进行比较表明，总体上在定性上是一致的，但是突出了模型混合过程的缺乏。

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