浅海内波及声场起伏数值研究

Ocean Internal Waves in ASIAEX 2001 and Numerical Simulation of Sound Propagation

为探讨声学方法监测 (反演 )海洋内波的可行性 ,分析ASIAEX2 0 0 1亚洲海海洋声学实验定点温度链实验数据 ,结果表明 :实验期间存在M 2内潮波、周期 10～ 3 0min非线性内波现象 ,并观测到双温跃层同相传播“双非线性内波”。分别对垂直和平行于内波传播方向传播声场进行了数值计算分析。垂直于内波传播方向的声传播计算结果表明 :简正波波数时间演化函数的频谱与内波引起的声速剖面变化频谱基本一致 ;简正波系数 (模值 )时间演化函数的频谱与内波引起的声源位置处的声速演化函数的频谱基本一致 ;高阶简正波波数差随时间的变化要比低阶简正波波数差小约 1个量级。平行于内波传播方向的声传播计算结果表明 :内潮波主要导致相邻简正波间耦合 ;非线性内波包能够导致跨号甚至垮多号简正波间耦合。讨论了 2种海洋内波声学监测方法。

The characters of ocean internal waves (IWs) are obtained by analyzing the ASIAEX2001 temperature data. The M2 internal tide, internal solitary wave packets with “periods”of 10-30min, and a couple of internal solitary wave packets are observed. The measured temperature data are used as input to the environmental models for numerical simulation of sound propagation. Numerical simulations are carried out for sound wave propagation which is perpendicular to and parallel with the propagating IWs, respactively. For the former, it is shown that the frequency spectra of the modal wave numbers and modal amplitudes are consistent with those for the sound speed fluctuation caused by IWs. For the later, it is shown that an internal tide causes adjacent (acoustic) mode coupling, but nonadjacent mode coupling can be caused by internal solitary wave packets. In this paper, the fluctuation of acoustic signals caused by linear IWs is also discussed. Two acoustic methods for monitoring ocean internal waves are presented.