西北太平洋副热带模态水形成区声传播特性分析

Acoustic propagation effect caused by subtropical mode water of northwestern Pacific

利用 Argo 剖面数据和水声学数值模型，分析了西北太平洋副热带模态水（STMW）形成区因季节性环境差异所引起的水声传播变化特征。声场计算结果表明，STMW 形成区域的声传播为近表层波导与会聚区的复合形式，其中会聚区终年存在，表面波导在秋、冬两季混合层加深的环境条件下出现，次表层波导在夏季 STMW 潜沉的环境条件下出现。上层海洋中两类不同形式的波导使表层和次表层的声能分布呈反相变化，波导内与波导外的声能差异可达10～15 dB（声波频率为1000 Hz）。STMW 的季节性变化还会引起会聚区的位置差异，具体情况与声源深度有关。声源在20 m 时，夏季会聚区距离最远，秋季、春季次之，冬季最近，夏季和冬季相差6．6 km；声源在150 m 时，夏季会聚区距离缩短了3．1 km，其他季节变化不大。

Acoustical propagation features caused by subtropical mode water （STMW）of Northwestern Pacific dur-ing seasonal transition are analyzed by Argo profile data and acoustic numerical model.The results of sound filed show that the main propagating pattern of STMW formed region is a combination of surface or subsurface duct and convergence zone （CZ）.The CZ exists all the year round,but the surface duct appears in a growing mixed-layer environment in autumn and winter,and the subsurface duct appears only in a STMW subduction environment in＆amp;nbsp;summer.Two types of duct propagation show an inverse pattern of sound energy distribution,and the difference can be around 10 to 15 dB between the internal and the external of the duct （sound frequency is 1 kHz）.Seasonal transition of STMW can also lead to the change of CZ positions.The changes are influenced by the source depth. When the source locates at 20 m,the CZ position reaches its furthest in the summer,remains medium in the spring,and arrives its nearest in the winter,where the maximum difference can be 6.6 km.When the source lo-cates at 150 m,the CZ reduces 3.1 km in summer and shows no distinct changes in other seasons.