相同尺度地形与背景流共振生成内孤立波机制

Mechanism of Internal Solitary Waves Generated by the Resonance of Same-scale Terrain and Background Current

为研究内孤立波的地形和背景流共振机制,用地形和背景流共振机制计算了3个潜标观测的内孤立波(不同模态、不同波长)的流速和传播速度,并与观测到的内孤立波进行比较。潜标观测的第一模态内孤立波(波长分别为6.4和3.3 km)都是下凹型内孤立波,2个内孤立波的传播速度约为1.4 m/s、最大振幅约为48 m,水平流向结构都是上层西北向、下层东南向,波长3.3 km的内孤立波波峰前后有更明显的下降流和上升流。用共振机制计算出的第一模态和第二模态纬向流速的垂向结构与观测相同,最大纬向流速出现的深度与观测一致,分别相差5和12 m。用共振机制计算出的内孤立波传播速度与用KdV方程计算的传播速度相当,共振机制计算波速为0.66~1.21 m/s,KdV方程计算波速为0.79~1.40 m/s。

The velocity and propagation characteristics of three internal solitary waves observed by mooring system are analyzed and compared with numerical experiments to study the resonance mechanism of terrain and background current.The mode-1 internal solitary waves(with wavelengths of 6.4 km and 3.3 km)are all concave internal solitary waves and have similar propagation speed and maximum amplitude.For horizontal flow direction structure,the flow in upper layer is northwestward while that in lower layer is southeastward.The downward and upward flow before and after the crest of internal solitary wave with wavelength of 3.3 km are more obvious.The vertical structure of zonal velocity of mode-1 and mode-2 internal solitary waves calculated based on resonance mechanism is basically consistent with the observation,and the depth of the maximum zonal velocity is comparable to the observed,the differences are 5 m and 12 m,respectively.The propagation speed of internal solitary wave calculated based on resonance mechanism is in the same order as calculated by the KdV equation,which are 0.66-1.21 m/s and 0.79-1.40 m/s,respectively.