The effect of friction and topography on coastal internal Kelvin waves at low latitudes
The effect of friction and topography on coastal internal Kelvin waves at low latitudes
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摩擦力和地形对低纬度沿海开尔文内波的影响
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
J. Allen
中科院分区：
文献类型：
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作者：
R. Romea;J. Allen
研究了海底Ekman层摩擦和坡度地形对层结海洋中自由传播的海岸内开尔文波的影响。假定摩擦效应很弱，并选择了特定的坡面地形，以便可以使用摄动法来获得解。采用了两种坡面地形模型：陡坡模型和弱坡模型，前者对应于低纬地区的Rossby半径尺度δR大于坡宽L S的情形，后者对应于δR≪L S的情形。在这两种情况下，内开尔文波都受到底部摩擦的抑制，并导致离岸和垂直相位滞后，以及岸上流动。然而，用两种不同的模型得到的结果有很大的不同。例如，对于陡坡情况，摩擦引起的垂直相移意味着表面的近岸速度v导致v低于v，而对于弱坡度情况，底部的运动导致v的下降。对于弱斜率，摩擦效应与海底速度成正比，这意味着对于中纬度地区，海底应力对斜压振型的影响很小。然而，陡坡模式的结果表明，斜压模式在低纬地区受到底部应力的显著影响。在这两种情况下，地形改变了波浪的频率和近岸相速度，改变了模式结构，并诱导了岸上流动。对于弱坡度情况，波速与Rossby半径尺度上平均底部深度成正比。对于陡峭的斜坡，波速的变化取决于斜坡几何图形的细节：向下凹的斜坡会增加速度，而向上凹的斜坡会降低速度。这两个模型都与秘鲁海岸的观测结果进行了比较。DOI：10.1111/j.1600-0870.1984.tb00256.x
The effects of bottom Ekman layer friction and slope topography on freely propagating coastal internal Kelvin waves in a stratified ocean are examined. Frictional effects are assumed weak and specific slope topographies are chosen so that perturbation methods may be used to obtain solutions. Two models for slope topography are utilized: a steep slope model, which corresponds to the low latitude case where the Rossby radius scale δ R is assumed large compared to the slope width L s , and a weak slope model, which corresponds to the case δ R ≪ L s . For both cases, internal Kelvin waves are damped by bottom friction, and offshore and vertical phase lags are induced, as well as an onshore flow. However, there are substantial differences between the results obtained with the two different models. For example, vertical phase shifts due to friction for the steep slope case imply that alongshore velocity v at the surface leads v below, while motions at the bottom lead for the weak slope case. For the weak slope, frictional effects are proportional to bottom velocity, implying that, for mid-latitudes, bottom stress effects on barocline modes are minimal. However, results from the steep slope model imply that baroclinic modes are significantly affected by bottom stress at low latitudes. In both cases, the topography changes the frequency and alongshore phase speed of the wave, the modal structure is altered, and an onshore flow is induced. For the weak slope case, the wave speed is proportional to the mean bottom depth averaged over the Rossby radius scale. For the steep slope, changes in wave speed depend on the details of the slope geometry: a slope that is concave downward increases the speed while a slope that is concave upward decreases the speed. Both models are compared with observations from the Peru coast. DOI: 10.1111/j.1600-0870.1984.tb00256.x