The evolution and energetics of large amplitude nonlinear internal waves on the Portuguese shelf
The evolution and energetics of large amplitude nonlinear internal waves on the Portuguese shelf
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DOI：
10.1357/002224001762842235
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发表时间：
2001-05
影响因子：
0.5
通讯作者：
D. Jeans;T. Sherwin
中科院分区：
文献类型：
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作者：
D. Jeans;T. Sherwin
1994 年 8 月对葡萄牙大陆架上的非线性内波进行了密集的现场观测，包括在同一波包在大陆架上传播时在三个位置进行了测量。这些波浪的特征是高达 45 m 的等温线突然下降，持续 10-35 分钟，伴随着高达 0.45 m s -1 的电流浪涌和超过 60 m 高达 0.7 m s -1 的剪切力。波远离陆架断裂传播，估计相速度为 0.57 m s -1 。波的振幅与理论最大值相当。波的动能和势能直接根据观察到的电流和密度结构计算。单个波与每单位波峰长度高达约 3.0 M J m -1 的总能量相关。陆架折断附近的陆架深度积分内波能量通量接近每单位波峰长度2000 W m -1 ，而在岸上则以大约7.7 × 10 -2 W m -2 的深度积分率下降。内波提供了垂直混合的重要来源，它们在 1994 年 8 月的大部分时间里都发生在葡萄牙陆架上，表现为持续的垂直涡流扩散率剖面，在 30 m 深度处达到 K z ≃ 2.2 × 10 -3 m 2 s -1 峰值。在葡萄牙陆架的任何模型中，必须通过这样的 K z 剖面来参数化内部混合，其中要准确地表示层结。
Intensive in-situ observations of nonlinear internal waves on the Portuguese shelf were made in August 1994, including measurements of the same wavepacket at three locations as it propagated on-shelf. The waves were characterized by sudden isotherm depressions of up to 45 m lasting 10-35 minutes, accompanied by current surges of up to 0.45 m s -1 and shears of up to 0.7 m s -1 over 60 m. The waves propagated away from the shelf break with an estimated phase speed of 0.57 m s -1 . The amplitude of the waves was comparable to the theoretical maximum. The kinetic and potential energies of the waves were calculated directly from the observed current and density structures. Individual waves were associated with a total energy of up to approximately 3.0 M J m -1 per unit crest length. The depth integrated on-shelf internal wave energy flux approached 2000 W m -1 per unit crest length near the shelf break and decreased on-shore at a depth integrated rate of approximately 7.7 × 10 -2 W m -2 . The internal waves provided an important source of vertical mixing where they occurred on the Portuguese shelf throughout most of August 1994, represented by a sustained vertical eddy diffusivity profile which peaked at K z ≃ 2.2 × 10 -3 m 2 s -1 at 30 m depth. Internal mixing would have to be parameterized by such a K z profile in any model of the Portuguese shelf in which the stratification were to be accurately represented.