西北太平洋中尺度涡合成结构及其对声传播的影响

Composed structure of mesoscale eddy in the Northwest Pacific Ocean and its influence on acoustic propagation

中尺度涡普遍存在于大洋中并会对声传播产生影响。利用2000—2018年AVISO卫星高度计资料和Argo浮标资料,通过涡旋合成方法构建了西北太平洋黑潮延伸体和亲潮延伸体海域中尺度涡的多年平均三维结构,对其垂直温、盐异常和声速特征进行分析,并采用Bellhop射线声学模型对中尺度涡背景下的声传播进行了模拟仿真。结果表明:1)冷涡背景下,温度异常为负,盐度异常在上层为负,在下层为正,声速等值线抬升;暖涡背景下,温度异常为正,盐度异常在上层为正,在下层为负,声速等值线下沉。2)冷涡背景下,声传播会聚区向声源方向偏移,会聚区宽度缩小;暖涡背景下,会聚区远离声源,会聚区宽度增大。声会聚区宽度在黑潮延伸体海域较在亲潮延伸体海域更大,距离声源也更远。3)冷涡背景下,声传播的反转深度变浅,暖涡背景下,反转深度加深;在黑潮延伸体海域,反转深度总体随经度增大而变浅,在亲潮延伸体海域则相反,反转深度随经度增大而变深。

Mesoscale eddies widely exist in the ocean and affect the sound propagation.Using AVISO altimeter and Argo buoy data from 2000 to 2018,the multi-year average three-dimensional structure of mesoscale eddies in the Kuroshio and Oyashio extension regions in the Northwest Pacific Ocean was constructed by synthesis method,and the structural characteristics of temperature anomalies,salt anomalies and sound velocity were analyzed.The sound propagation in eddies is simulated by using Bellhop ray acoustic model.The results show that:(1)Under the background of the cold eddy,the temperature anomaly is negative,the salinity anomaly is negative in the upper layer and positive in the lower layer,and the sound velocity contour rises.Under the background of warm eddy,the temperature anomaly is positive,the salinity anomaly is positive in the upper layer and negative in the lower layer,and the sound velocity contour is sinking.(2)The cold eddies cause the convergence region to shift towards the sound source direction and the width of convergence zone to decrease;the warm eddies cause the convergence zone to move away from the sound source and increase its width.The convergence area in the Kuroshio extension region is wider than that in the Oyashio extension region,and is further away from the sound source.(3)The cold eddies make the convergence zone turning depth shallower,while the warm eddies make the convergence zone turning depth deeper.In the Kuroshio extension region,the inversion depth is shallower with the increase of longitude,but in the Oyashio extension region,the inversion depth is deeper with the increase of longitude.