Nearshore currents off Long Island
Nearshore currents off Long Island
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长岛附近的近岸洋流
DOI：
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发表时间：
1976
期刊：
影响因子：
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通讯作者：
G. Csanady
中科院分区：
文献类型：
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作者：
J. Scott;G. Csanady
1975年9月，在长岛以南11公里处（水深32米），使用电磁海流计在三个水层对海流进行了为期25天的观测。发现潮流强度适中，约为20厘米/秒。非潮流是由风应力、淡水流入导致的水平密度差异以及向西南倾斜的沿岸水面坡度引起的。时间平均流具有简单的特征，用经典的埃克曼摩擦平衡模型就能充分描述。通过对平均周期进行适当调整，从数据中推导出了底部摩擦系数和沿岸压力梯度的定量估计值。底部摩擦系数与根据边界层理论对约70厘米高的粗糙元所做的估计相符。从海流行为推导出的沿岸压力梯度与大地测量水准测量的结果一致。
Currents were observed for a 25-day period in September 1975 at 11 km south of Long Island, where the water is 32 m deep, at three levels by using electromagnetic current meters. Tidal currents were found to be moderately strong, of the order of 20 cm s−1. Nontidal flow is caused by wind stress, horizontal density contrasts due to fresh water influx, and a longshore surface level gradient sloping down south-westward. The time-averaged flow has simple characteristics, adequately described by classical Ekman models in frictional equilibrium. By suitable changes in the averaging period, quantitative estimates of a bottom friction coefficient and a longshore pressure gradient are deduced from the data. The bottom friction coefficient agrees with what one would estimate from boundary layer theory for roughness elements of about 70-cm height. The longshore pressure gradient deduced from the behavior of currents agrees with the evidence of geodetic leveling.