Using temperature-salinity profiles and current measurements,satellite data and reanalysis data in April 2018,this study analyses the acoustic field characteristics and effects of an abnormal anticyclonic eddy(AAE)on acoustic propagation on the continental slope area in the northwestern South China Sea(SCS).The results show that the AAE has a lens-shaped structure with a surface cold core,a shallower mixed layer,and subsurface intensi-fied velocities.Unlike the concave sound-speed contours in the normal anticyclonic eddy(NAE),the sound-speed distribution in the abnormal anticyclonic eddy(AAE)exhibits a lens-shaped structure with an upward convexity and downward concavity.The surface sound speed within the eddy is lower than that outside,showing a negative anomaly(＜-2 m/s).Conversely,the sound speed in the subsurface layer of the eddy is higher than that outside,showing a positive anomaly(＞11 m/s).This results in the thickness of the original double thermocline extending up and down by a total of 47 meters in the presence of the eddy.As the sound propagates from the eddy outside on the shelf to the deep sea,the surface sound channel disappears as the propagation distances decreasing in the AAE,con-trast to the increased distance in the NAE.As the sound propagates from the eddy outside in the deep ocean to the shelf,the location of the sound energy convergence zone moves backward and downward in the AAE,with the max-imum distance exceeding 24 km and 0.3 km,respectively.This is similar to the situation in the NAE.As the sound propagates from the eddy core to outside in the deep sea,the turning depth of the sound deepens and the distance between the sound energy convergence zones doubles in the AAE,while no changes in the NAE.
关键词
异常反气旋涡/水下声传播/汇聚区/南海西北陆坡
Key words
abnormal anticyclonic eddy/underwater sound propagation/convergence zone/northwest continental slope of the South China Sea
维普
万方数据