Bruce D. Cornuelle
Mail Code 0230, Scripps Inst. of Oceanogr., Univ. of California at San Diego, La Jolla, CA 92093-0230
Geometric rays were traced for a variety of source--receiver configurations in the test ocean sound-speed field constructed for the 124th Meeting of the Acoustical Society of America. A stochastic inverse incorporating the statistical information distributed with the test ocean was performed using only one-way travel times as data. Realistic errors in travel times and source--receiver positions were allowed for. The travel times were assumed to be contaminated with internal-wave-induced travel time fluctuations. The fluctuation variance increased linearly with range, with a magnitude of 10 ms rms at 1000 km. This internal wave noise can be reduced by a factor of N[sup -1/2] by assuming that the mesoscale sound-speed structure remains static over N internal-wave-induced decorrelation times. Decorrelation times shorter than 10 min have been observed in the North Pacific at 1000-km range, so a daily average can yield a net contamination below 1 ms, neglecting the effects of longer period fluctuations like internal tides. The simulation results are sensitive to the size of the assumed error, and using values below 1 ms can lead to unrealistically good performance. The size of the source--receiver position errors can vary dramatically depending on the navigational techniques used and can have significant effects on the array design problem. These sensitivities will be explored in the process of choosing a source--receiver array adequate to resolve 96% of the sound-speed variance at 700-m depth in the test ocean.