Computed and observed currents, elevations, and salinity in a branching estuary
Computed and observed currents, elevations, and salinity in a branching estuary
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计算和观测分支河口的水流、海拔和盐度
DOI：
10.2307/1351582
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
J. Stephens
中科院分区：
文献类型：
--
作者：
R. Uncles;J. Stephens
添马舰河口的一维流体动力学模型与实测的潮汐高度和海流吻合良好。计算电流用于驱动盐平衡的一维移动元件模型。移动单元模型克服了与强潮汐平流相关的数值困难。在高水位的盐度轴向分布，使用移动元件模型计算，比较以及与测量。模拟和观察到的高水盐度分布在这个大潮汐河口的潮差的依赖性很小。盐度的主要变化是由于径流。这种对径流的强烈和快速依赖是短停留（或冲洗）时间的结果。通常，在河口上游10公里处，全年的停留时间不到一天。整个河口的停留时间在夏季达到最大值，为14 d.在高径流冬季期间停留时间小于5天。动元盐度模型的混合系数推导出盐度测量。在固定位置的扩散系数沿着河口的盐度模型的解决方案推导出来。对于平均径流，平均大潮和小潮的空间平均系数分别为180和240 m2 s-1。因此，在分散的春-小潮变化是相当小的，并显示出与潮差的负相关。对于典型的夏季和冬季径流，平均潮汐的空间平均弥散系数分别为150至300 m2 s−1。分散与径流的增加和减少与潮差意味着浮力驱动的电流产生的剪切分散在这个河口的一个重要组成部分。
A one-dimensional, hydrodynamical model of the Tamar Estuary shows good agreement with measured tidal elevations and currents. Computed currents are used to drive a one-dimensional moving-element model of the salt balance. The moving-element model overcomes the numerical difficulties associated with strong tidal advection. Axial distributions of salinity at high water, computed using the moving-element model, compare well with measurements. The modelled and observed high water salinity distributions in this macrotidal estuary show little dependence on tidal range. The major variability in salinity is due to runoff. This strong and rapid dependence on runoff is a consequence of short residence (or flushing) times. Typically, residence times are less than one day throughout the year in the upper 10 km of estuary. The residence times maximize in summer, reaching 14 d for the whole estuary. During high runoff winter periods residence times are less than 5 d. Mixing coefficients for the moving-element salinity model are deduced from salinity measurements. Dispersion coefficients at fixed locations along the estuary are deduced from solutions of the salinity model. The spatially-averaged coefficients at mean spring and neap tides are 180 and 240 m2 s−1, respectively, for average runoff. Therefore, spring-neap variations in dispersion are fairly small and show a negative correlation with tidal range. The spatially-averaged dispersion coefficients at mean tides vary from 150 to 300 m2 s−1 for typical summer and winter runoff, respectively. The increase in dispersion with runoff and the decrease with tidal range implies that buoyancy-driven currents generate an important component of the shear dispersion in this estuary.