Intrinsic Nonlinearity and Spectral Structure of Internal Tides at an Idealized Mid-Atlantic Bight Shelf Break
Intrinsic Nonlinearity and Spectral Structure of Internal Tides at an Idealized Mid-Atlantic Bight Shelf Break
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理想化的中大西洋湾陆架断裂处内潮汐的固有非线性和频谱结构
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
T. Duda
中科院分区：
文献类型：
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作者：
W. Zhang;T. Duda
为了量化中大西洋海湾陆架破裂处内潮产生的动力学特征，本研究采用了一个理想的海洋模式，该模式由夏季气候学层结和近岸边界的单色正压潮流强迫而成。该情景的弗劳德数为亚单位，陆架断裂的近海测深斜率为超临界。正压到斜压的能量转换率为335Wm−1，其中14%的能量通过湍流和底摩擦局部耗散，18%的能量辐射到陆架上。与以前的研究一致，非线性效应会在陆架断裂处产生额外的超谐和亚谐内波。亚谐波是亚惯性的、瞬息万变的，在强迫频率下主要被困在狭窄的内波波束中。它们很可能是与强非线性相关的非共振三元相互作用的结果。与亚谐波相关的强垂直切变有增强作用的趋势。
AbstractTo quantify dynamical aspects of internal-tide generation at the Mid-Atlantic Bight shelf break, this study employs an idealized ocean model initialized by climatological summertime stratification and forced by monochromatic barotropic tidal currents at the offshore boundary. The Froude number of the scenario is subunity, and the bathymetric slope offshore of the shelf break is supercritical. A barotropic-to-baroclinic energy conversion rate of 335 W m−1 is found, with 14% of the energy locally dissipated through turbulence and bottom friction and 18% radiated onto the shelf. Consistent with prior studies, nonlinear effects result in additional super- and subharmonic internal waves at the shelf break. The subharmonic waves are subinertial, evanescent, and mostly trapped within a narrow beam of internal waves at the forcing frequency. They likely result from nonresonant triad interaction associated with strong nonlinearity. Strong vertical shear associated with the subharmonic waves tends to enhanc...