Reflection and diffraction of internal solitary waves by a circular island
Reflection and diffraction of internal solitary waves by a circular island
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DOI：
10.1007/s10872-006-0100-4
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发表时间：
2006-12
影响因子：
2.3
通讯作者：
S. Chao;P. Shaw;M. Hsu;Ying-Jang Yang
中科院分区：
文献类型：
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作者：
S. Chao;P. Shaw;M. Hsu;Ying-Jang Yang
利用三维非静力数值模式研究了一阶和二阶孤立波在岛屿上的反射和绕射。模型域由300米深的海洋中直径15公里的圆形岛屿组成。我们使用规定的密度异常，在最初静止的海洋产生高能量的内部孤立波，其随后的传播受到岛屿扰动与地球自转的影响。除了反射波外，还有两个波支绕过岛屿并在岛屿后方重新连接，岛屿扰动对第一模态和第二模态波的影响在性质上相似，但由于接触时间较长，以及在地球自转的情况下，第二斜压模态的Rossby半径与岛屿直径之间的尺度相容性，岛屿扰动对第一模态和第二模态波的影响更为深刻。在没有地球自转的情况下，反射波和衍射波相对于通过岛中心的纵轴是对称的。随着地球的自转，由于科里奥利偏转，跟随波前的电流向右偏转。对于向西传播的入射波，偏转有利于在交叉点和岛屿之间的区域中向北传播波，将波重连点向北移动到岛屿后面。它还将反射波中最明显的部分移向东南方向。在地球自转的情况下，第二模式的入射波会产生岛状的内部开尔文波，在波前通过后可以看到。
We have investigated the reflection and diffraction of first-mode and second-mode solitary waves by an island, using a three-dimensional nonhydrostatic numerical model. The model domain consists of a circular island 15 km in diameter in an ocean 300 m deep. We use prescribed density anomalies in an initially motionless ocean to produce highly energetic internal solitary waves; their subsequent propagation is subject to island perturbations with and without the effect of earth’s rotation. In addition to reflected waves, two wave branches pass around the island and reconnect behind it. Island perturbations to the first-mode and second-mode waves are qualitatively similar, but the latter is more profound because of the longer contact time and, in the presence of earth’s rotation, the scale compatibility between Rossby radius of the second baroclinic mode and the island diameter. Without earth’s rotation, reflected and diffracted waves are symmetrical relative to the longitudinal axis passing through the island center. With earth’s rotation, the current following the wave front veers to the right due to Coriolis deflection. For a westward propagating incoming wave, the deflection favors northward wave propagation in the region between the crossover point and the island, shifting the wave reconnection point behind the island northward. It also displaces the most visible part of the reflected waves to the southeast. In the presence of earth’s rotation, a second-mode incoming wave produces island-trapped internal Kelvin waves, which are visible after the passage of the wave front.