Ocean acoustic tomography from ships
Ocean acoustic tomography from ships
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DOI：
10.1029/jc094ic05p06232
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发表时间：
1989-05
影响因子：
--
通讯作者：
B. Cornuelle;W. Munk;P. Worcester
中科院分区：
文献类型：
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作者：
B. Cornuelle;W. Munk;P. Worcester
在1000×1000 km范围内通过海洋声层析成像进行海洋声速场的中尺度制图，通过增加几个声系泊装置和一个可移动的船载接收机得到了极大的增强。在最严重斜压模式扰动的海洋中，基于测量声传播时间内实际噪声水平的计算机模拟给出了四（六个）声源系泊在ΔC（x;y,z）中5%（1%）的剩余方差。相比之下，基于传统垂直剖面的物镜测绘需要3倍的蒸距才能产生等效的残差。详细的结果取决于许多参数：假设的中尺度频谱和垂直模式结构，观测到的多路径数量，系泊配置，船站数量和走时信号电平（由于中尺度涡流）和噪声电平（由于内波和位置保持误差）。这些参数有临界值，低于临界值有明显的退化，超过临界值则几乎没有增益。我们认为在实践中可以达到临界值，因此对中尺度制图的最终限制是由内波引起的走时误差施加的。这假设通过卫星导航和高频声学相结合来保持淹没声源和接收器的位置可以达到±10米的精度。本研究假设海洋是静止的；第二篇论文将讨论产生电流的相互传输，从而讨论正压模式。在动态海洋模型中，这是估算ΔC（x,y,z;t）所必需的。所有这些都是为1988-1989年在格陵兰海进行断层扫描实验做准备。
Mesoscale mapping of the ocean sound speed field in a 1000×1000 km area by means of ocean acoustic tomography is greatly enhanced by augmenting a few acoustic moorings with a movable ship-based receiver. Computer simulations based on realistic noise levels in the measured acoustic travel times give 5% (1%) residual variance in ΔC(x;y,z) for four (six) acoustic source moorings in an ocean perturbed in the gravest baroclinic mode. For comparison, objective mapping based on traditional vertical profiles requires 3 times the steaming distance to yield equivalent residual error. Detailed results depend on many parameters: the assumed mesoscale spectrum and vertical mode structure, the number of observed multipaths, the mooring configuration, the number of ship stations and the travel time signal level (due to mesoscale eddies) and noise level (due to internal waves and position-keeping errors). These parameters have critical values, below which there is distinct deterioration and beyond which there is little gain. We believe that the critical values can be attained in practice so the ultimate limit on mesoscale mapping is imposed by the internal wave-induced travel time error. This assumes that position keeping of the submerged acoustic sources and receiver by a combination of satellite navigation and high-frequency acoustics can be achieved with ±10-m accuracy. The present study assumes a stationary ocean; a second paper will deal with reciprocal transmissions yielding currents and hence the barotropic mode. This is required in a dynamic ocean model for estimating ΔC(x,y,z;t). All this is preparatory to a tomography experiment in the Greenland Sea in 1988–1989.