Modeling tidal exchange and dispersion in Boston Harbor
Modeling tidal exchange and dispersion in Boston Harbor
复制标题
DOI：
10.1029/92jc01429
复制
发表时间：
1992-10
影响因子：
--
通讯作者：
R. Signell;B. Butman
中科院分区：
文献类型：
--
作者：
R. Signell;B. Butman
潮汐分散和水在波士顿港和周围海洋之间的水平交换用高分辨率（200米）深度平均数值模型进行了检查。海港的深度和海岸线几何形状的强烈变化在模拟的潮流中产生了复杂的空间格局，这些格局通过船载声学多普勒测量得到了验证。拉格朗日交换实验表明，由于涨潮/退潮响应的不对称性，潮汐流在港口入口附近快速交换和混合物质。这个潮汐混合带大致从入口延伸出潮汐偏移，在港口的整体冲刷中起着重要作用。然而，由于潮汐只能在这个有限的区域内有效地混合物质，因此必须将港口冲刷视为一个两步过程：在潮汐混合带内快速交换，然后由非潮汐残余流冲刷潮汐混合带。因此，仅根据潮汐计算来估计围堰冲厕的时间，可能会大大高估在典型环境条件下预期的冲厕时间。来自点源的粒子释放模拟也表明，虽然潮汐在入口附近有效地交换物质，但来自点源的分散的确切性质对释放的时间和位置极为敏感，并且粒子的分布是条纹状和斑块状的。这表明，必须明确地对这些地区的点源色散进行高分辨率模拟，而不能将其参数化为更大尺度流场中的高斯扩散羽流。
Tidal dispersion and the horizontal exchange of water between Boston Harbor and the surrounding ocean are examined with a high-resolution (200 m) depth-averaged numerical model. The strongly varying bathymetry and coastline geometry of the harbor generate complex spatial patterns in the modeled tidal currents which are verified by shipboard acoustic Doppler surveys. Lagrangian exchange experiments demonstrate that tidal currents rapidly exchange and mix material near the inlets of the harbor due to asymmetry in the ebb/flood response. This tidal mixing zone extends roughly a tidal excursion from the inlets and plays an important role in the overall flushing of the harbor. Because the tides can only efficiently mix material in this limited region, however, harbor flushing must be considered a two step process: rapid exchange in the tidal mixing zone, followed by flushing of the tidal mixing zone by nontidal residual currents. Estimates of embayment flushing based on tidal calculations alone therefore can significantly overestimate the flushing time that would be expected under typical environmental conditions. Particle-release simulations from point sources also demonstrate that while the tides efficiently exchange material in the vicinity of the inlets, the exact nature of dispersion from point sources is extremely sensitive to the timing and location of the release, and the distribution of particles is streaky and patchlike. This suggests that high-resolution modeling of dispersion from point sources in these regions must be performed explicitly and cannot be parameterized as a plume with Gaussian-spreading in a larger scale flow field.