背景流与地形对海洋内波影响初探

Preliminary study of background current and topography offects on ocean internal wave

采用Boussinesq近似,研制了准三维、非线性、非静力的斜压数值模式。利用该模式做了背景流与海底地形对高频海洋内波影响的数值试验。本文得到的主要结论有:各数值试验初始1小时内,有适应过程,并最终形成垂直方向为单圈环流的海洋内波波包;以后进入海洋内波的演变过程,并在非线性作用下形成椭圆余弦波波包,并向孤立内波演变。当无背景流时,地形会激发出两支传播方向相反的海洋内波波包,水深大处波包传播较慢。当存在定常背景流时,在其与地形共同作用下,在地形处会激发出较强的内波波包,若地形足够陡峭,则内波波包截陷于该陡峭处,造成该处强烈的垂直运动。背景流随时间的变化会对在台阶地形跃阶处的内波波包产生不同的影响。

Base on Boussinesq approximation,a quasi-three-dimensional,nonlinear,non-static baroclinic numerical model was developed and used to study the effects of background currents and topography on the high-frequency oceanic internal wave.The main conclusions include： the adaptation process lasts for an hour and then the single-circle internal wave packet occurs in the vertical for each numerical experiment;.during the evolution process of ocean internal wave,the internal wave was steepened into oval cosine waveform via the nonlinear effects.Without the constant background currents,topography effects could trigger two wave packages propagating in the opposite direction and wave packet propagate slower in deep water than that in shallow water.With the constant background currents,strong internal wave packages are generated under the influence of topography and background current.When the terrain is steep enough,the internal wave packets are trapped in this region,resulting in strong vertical motions.When background current changes with time,it has different effects on internal wave packet in the step-like topography.