西沙海槽海域声速特点分析

Analysis on the character of sound velocity in the Xisha Zone

通过对西沙海槽海域实测的58个声速剖面进行分析研究,认为区内声速剖面具有典型的三层结构特征-表面层、中间跃变层以及深海恒温层。表面层普遍有声速稳定次层,平均厚度约18.6m,表层声速最大值一般出现在下午3点至4点之间,最小值则出现在早上6点至7点之间。声速极小值出现在跃变层与深海恒温层间的过渡水层,其深度最浅为830.7m,平均深度为1220m,但当水深大于1300m以后,声速与水深成线性相关,声速梯度稳定,平均为每百米1.34m/s。

Based on the study of the fifty eight sound velocity profiles,the character of sound velocity in the Xisha Zone is the representative structure of 3-layers,which are the sound stable surface,springing layer in the middle and deep sea temperature invariable layer.There is one sub-layer,where the sound velocity has no change or only litte change in the sound stable surface,the average thickness is 18.6 m.The maximum and the minimum velocity in this layer may be occurred during the 15：00 to 16：00 in th afternoon and 06：00 to 07：00 in the morning respectively.The infinitesimal velocity occurred between the the springing layer and the deep sea temperature invariable layer,the minimum depth is 830.7 m,and the average depth is 1 220 m.The velocity and the depth are linear correlation,the sound velocity increased with the depth,and the average grad is 1.34 m/s evey hundred.