声强干涉结构监测浅海温跃层深度起伏

Acoustic monitoring of the thermocline height by acoustic intensity interference-pattern

浅海声场声强谱存在干涉结构,在声源和接收器固定的情况下,声强干涉谱与海洋环境参数存在对应关系.应用声强干涉结构信息监测浅海温跃层深度起伏,在温跃层初始深度已知的情况下(温盐深仪或声速仪测量得到),利用单水听器记录宽带信号干涉谱的时变结构反演得到浅海温跃层深度随时间变化.数值仿真验证了方法的有效性并应用于05黄海内波与锋面声传播起伏实验(AEYFI-05:Acoustics Experiment of Yellow Sea Oceanic Front and Internal Waves2005)数据.考虑传播路径的水平变化特性,引入绝热近似修正使得反演精度明显提高,温跃层深度起伏反演结果与温度链实测结果吻合良好.该方法可用在夏秋季环境下的强温跃层深度时变特征监测.

Relationship between water depth and acoustic intensity interference-pattern in a shallow water environment with a homogeneous SSP was proposed by D.E.Weston many years ago.In this paper,we extend the idea to monitor temporal variation of thermocline position by combining the concept of up turning depth for lower order normal modes.Broadband signal is used and acquired with only single hydrophone.To validate the idea,both simulation and AEYFI-05（Acoustics Experiment of Yellow sea Oceanic Front and Internal Waves 2005）experiment data processing are performed.In the AEYFI-05 experiment,broadband signals were transmitted from a fixed source and received at fixed receivers located at 37 km along a cross-shelf propagation track.The acoustic intensity pattern indicates regular frequency shift that is used to predict the variation of thermocline position monitored by a thermistor chain at the same time.Taking into account of adiabatic approximation,an excellent agreement between inverted thermocline position and that monitored by the thermistor chain suggests a potential of long-term acoustic monitoring of the thermocline position in summer conditions.