Research On Sound Scattering Layer In The Western Pacific Observed With Multibeam Sounding System And Ship-board ADCP

In recent years,the study of acoustic scattering layer in the Western Pacific has gradually became one of the hot research topics.In this paper,echo intensity data of 38kHz Ship-board ADCP and 12kHz Multibeam echo sounder in water image data package collected by two different voyages are used to focuses on the study of the acoustic volume back scattering intensity of the Western Pacific Ocean.This paper mainly includes the following three aspects:(1)Double scattering layer exists in the Western Pacific,the upper scattering layer is located in 0?200m,and the deep scattering layer is located at 400?600m,the two methods can be used to observe the existence of the upper and the deep scattering layers and their characters of vertical variation and diurnal variation.The intensity of the upper scattering layer is weak during the daytime but it's strong at night.On the contrary,the diurnal variation of the deep scattering layer is different from the upper scattering layer.The migration of scattering layers is consistent with the vertical migration of zooplankton.The biological composition of the Western Pacific Ocean and its uneven distribution of the individual species are analyzed and discussed.Because of this,the two kinds of measurement methods can be used to observe the two scattering layer in the Western Pacific Ocean.(2)There are differences between the observed results measured by multibeam echo sounder and ADCP.The depth of migration is not uniform observed by multibeam echo sounder when the scatterer migrates to the deep scattering layer.This phenomenon lead to the diurnal variation characteristics of scattering layer thickness.(During the daytime,the thickness of the deep scattering layer changes thicker at daytime and thiner at night).However,due to the limitation of the range,the ship-board ADCP is not able to observe this phenomenon.(3)In the north latitude areas of the Western Pacific Ocean,the intensity of the scattering layer is positively correlated with the latitude.The intensity of the scattering layer is stronger in the high latitude areas,and weaker in the low latitude areas.The causes of this phenomenon are analyzed in this paper.