孤子内波导致海洋环境噪声垂直指向性异常分析

依据近场波数积分、远场耦合简正波相结合的二维噪声场模型,侧重理论研究孤子内波所在扇区,环境噪声垂直阵响应的变化,分析了某些孤子内波情形下垂直阵环境噪声水平凹槽变深这一异常现象的原因:孤子内波离垂直阵较近时,远离内波的海面噪声源多,其激发的简正波能量由低号耦合到高号,在垂直阵处高号简正波能量对环境噪声场贡献增大,导致环境噪声水平凹槽加深;对于大尺度、多波包孤子内波,其范围相对较大,内波所在区的局部简正波本征值和本征函数产生的变化影响显著,使低号简正波衰减变快,而高号衰减慢,导致接收阵处高号简正波能量增加,低号简正波变弱,这样,无论孤子内波群靠近或离接收阵远,都将使垂直阵环境噪声水平凹槽加深。 

Analysis of the abnormality of the ocean ambient noise vertical directionality caused by solitary waves

According to the two-dimension ambient noise model which combines wave number integral method (near field) and normal mode method (far field), the theoretical studies on the variation of the vertical array response to ambient noise in the region where the solitary waves exist are oriented. The reasons are analyzed theoretically for the "abnormal" phenomenon that notch in the horizontal direction of the vertical directionality of ambient noise becomes deeper when some solitary waves exist: when the solitary waves are close to the vertical array, the noise sources far from the solitary waves increase, the energy are converted from the lower order modes into the higher order modes, the contribution of higher order modes increases at the vertical array for ambient noise, the notch become deeper. When the vast-scale and multi-packets solitary waves exist, their region is relatively large. The influence of the changes of local eigenvalues and eigenfunctions in this region are remarkable. The attenuations of the lower order modes become faster, however, the higher ones become slower. The energy of higher order modes increases at the vertical array, so the noise notch become deeper no matter where the solitary waves are.