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Acoustic shadow-zone arrivals at long range in the North Pacific Ocean.

机译：北太平洋大范围的声影区到达。

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摘要

Deep acoustic shadow-zone arrivals were first observed on horizontal, bottom-mounted receiving arrays in the North Pacific Ocean in the late 1990s. These receptions revealed significant acoustic energy penetrating an estimated 500-1000 m into geometric shadow zones below cusps (caustics) of predicted timefronts, much more than predicted by diffraction theory. Two vertical line array receivers deployed in close proximity in the North Pacific as part of the SPICEX experiment, together virtually spanning the water column, show the vertical structure of the shadow-zone arrivals for transmissions from broadband 250-Hz acoustic sources moored at the sound channel axis (750 m) and slightly above the surface conjugate depth (3000 m) at ranges of 500 and 1000 km. Chapter II compares a daily average of acoustic timefronts with parabolic equation simulations based on a sound-speed profile measured nearly concurrently with the acoustic data acquisition. Simulations incorporating a range-independent sound-speed profile confirmed the presence of deep shadow-zone arrivals. Receptions from off-axis sources also revealed acoustic energy scattering back up toward the axis at the end of the timefront, referred to as axial shadow-zone arrivals. Simulations incorporating sound-speed fluctuations consistent with the Garrett-Munk internal-wave energy spectrum at full strength accurately predict the vertical extent of and energy contained in both axial and deep shadow-zone arrivals. Chapter III extends the analysis to include acoustic receptions from June to November 2004. Incoherent monthly averages of acoustic timefronts indicate that lower cusps associated with acoustic rays with shallow upper turning points (UTPs), where sound-speed structure is most variable and seasonally dependent, deepen from June to October as the summer thermocline develops. Surface-reflected rays, or those with near-surface UTPs, exhibit less scattering due to internal waves than in later months, when the UTP deepens. Data collected in November exhibits dramatically more vertical extension than previous months. The depth to which the timefronts extend as the seasons change is a complex combination of deterministic changes in the depths of the lower cusps as the range-average profiles evolve and of the amount of scattering, which depends on the depths of the UTPs and the mean vertical gradients at those depths.
机译：1990年代后期，在北太平洋的水平，底部安装的接收阵列上首次观察到深声影带到达。这些接收结果显示，巨大的声能穿透了预计的时间段的尖端（焦散）下方约500-1000 m的几何阴影区域，远远超过了衍射理论所预测的范围。作为SPICEX实验的一部分，在北太平洋部署了两个垂直线阵接收器，它们实际上跨过水柱，显示了阴影区到达的垂直结构，用于从停泊在声音中的宽带250 Hz声源进行传输通道轴（750 m），并在500和1000 km范围内略高于表面共轭深度（3000 m）。第二章将声学时线的日均平均值与抛物线方程仿真进行了比较，该抛物线方程仿真基于与声波数据采集几乎同时测量的声速曲线。结合了与范围无关的声速曲线的仿真证实了存在深阴影区。从离轴源接收到的信号还表明，声波能量的散射在时间前期结束时又朝着轴方向散射，这称为轴向阴影区到达。包含与Garrett-Munk内部波能谱在全强度下一致的声速波动的模拟，可以准确预测轴向和深阴影区域到达的垂直范围以及所包含的能量。第三章将分析范围扩大到2004年6月至2004年11月的声音接收。不连续的每月声音时间平均值表明，与具有较浅的上转折点（UTP）的声线相关的较低的尖点，其中声速结构变化最大，并随季节变化，随着夏季温床的发展，从六月到十月加深。当UTP加深时，与后几个月相比，表面反射的射线或具有近表面UTP的射线由于内部波而显示的散射较少。与前几个月相比，11月份收集的数据显示出更大的垂直扩展。随着季节变化，时间前沿延伸到的深度是随着范围平均轮廓的演变，下尖尖深度的确定性变化和散射量的复杂组合，这取决于UTP的深度和均值在这些深度的垂直渐变。

著录项

  • 作者

    Van Uffelen, Lora J.;

  • 作者单位

    University of California, San Diego.;

  • 授予单位 University of California, San Diego.;
  • 学科 Physical Oceanography.;Physics Acoustics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 107 p.
  • 总页数 107
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 海洋物理学;声学;
  • 关键词

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