Tidal Modulation of Surface Gravity Waves in the Gulf of Maine
Tidal Modulation of Surface Gravity Waves in the Gulf of Maine
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DOI：
10.1175/jpo-d-17-0250.1
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发表时间：
2018-10
影响因子：
3.5
通讯作者：
Pengcheng Wang;J. Sheng
中科院分区：
文献类型：
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作者：
Pengcheng Wang;J. Sheng
本研究利用现场观测和数值模型结果研究了缅因湾 (GoM) 表面重力波的潮汐调制。观测数据分析表明，该地区以涌浪为主的波浪的平均波浪变量存在显着的半日潮汐调制。观测到的潮汐调制具有显着的时空变化，在墨西哥湾口附近幅度较大。观测结果还表明，在接下来的潮流中，有效波高 Hs 的最大调制时间不寻常。耦合波环流模型成功地再现了观测到的潮汐调制和相关的时空变化。模型结果表明，最大 Hs 调制首先在墨西哥湾口附近的最大涨潮或落潮期间产生，然后传播到内湾。在墨西哥湾口周围，潮汐流具有较强的空间梯度，导致海流引起的会聚、折射和波数偏移的影响很大。会聚产生的潮汐调制 (10%~14%) 受波传播方向的影响小于波数偏移 (6%~10%) 和折射 (4%~20%) 产生的调制。后者的调制随着波传播方向的变化而显着变化。此外，电流增强耗散在强风期间变得很重要，这会减少研究期间至少一半的 Hs 调制。在随后的潮汐流中观察到的最大 Hs 调制的异常时间主要可以通过与波能收敛和空间减速流中从电流到波的能量转移相关的收敛和波数移动来解释。
This study examines the tidal modulation of surface gravity waves in the Gulf of Maine (GoM) by using in situ observations and numerical model results. Analysis of observational data demonstrates significant semidiurnal tidal modulations in the mean wave variables for swell-dominated waves in the region. The observed tidal modulation features significant spatial–temporal variabilities, with large magnitudes near the mouth of the GoM. Observations also demonstrate unusual timing of the maximum modulation of significant wave height Hs in the following tidal currents. The coupled wave–circulation model successfully reproduces the observed tidal modulation and the associated spatial–temporal variabilities. Model results demonstrate that the maximum Hs modulations are first generated during the maximum flood tide or ebb tide near the mouth of the GoM and then propagate onto the inner gulf. Around the mouth of the GoM, tidal currents have strong spatial gradients, resulting in great effects of current-induced convergence, refraction, and wavenumber shift. The tidal modulation in Hs generated by convergence (10%–14%) is less affected by the wave propagation direction than the modulation generated by the wavenumber shift (6%–10%) and refraction (4%–20%). The latter modulation varies significantly with changes in the wave propagation direction. In addition, current-enhanced dissipation becomes important during high winds, which reduces at least one-half of the Hs modulation during the study period. The observed unusual timing of the maximum Hs modulation in the following tidal currents can be mostly explained by the convergence and wavenumber shift associated with wave-energy convergence and energy transfer from currents to waves in spatially decelerating currents.