基于船载ADCP和LADCP观测的南海声散射层

Research on Sound Scattering Layer in the South China Sea Observed With Ship-board ADCP and LADCP

依据2012年ROSE航次船载ADCP和LADCP的观测数据,对南海秋季声散射层的垂向分布特征和日变化进行了分析;根据估算出的散射层中散射体的垂向迁移速度,对散射体类型进行了分析。观测结果表明,南海存在着2个声散射层,一个声散射层位于0～200m,散射强度具有显著的日变化特征,即白天弱,夜晚强;另一声散射层则处于300～500m的深度,其散射强度的日变化与另一个相反,白天较强,夜晚变弱。通过计算可得,散射体的垂向迁移,在傍晚时分运动方向向上,速度约为1.74cm/s;而凌晨左右运动方向向下,速度约为1.39cm/s。观测结果还表明,ADCP和LADCP的观测结果能够互相补充,更有利于对声散射层的细致研究。

The vertical distribution feature and diurnal variation of sound scattering layers in the South China Sea were analyzed with the data obtained by the ship-board ADCP and LADCP during an autumn cruise of the ROSE（Responses of Marine Hazards to Climate Change in the Western Pacific）project in 2012.The scatterers in the scattering layer were categorized by the estimates of their vertical speeds.The measurements showed the existence of two sound scattering layers at two depths,0~200mand 300~500m.Significant diurnal variation was observed in the shallower scattering layer,with weak strength in daytime and strong in nighttime.While this diurnal variation was reversed in the deeper counterpart,with strong strength in daytime and weak in nighttime.The vertical moving velocities of the scatterers were also estimated,with an ascending velocity of around 1.74cm/s at nightfall and a descending velocity of around1.39cm/s before dawn.The analysis also showed that the measurements made by ADCP and LADCP could well complement each other,which benefits the study on sound scattering layer.