### ASA 126th Meeting Denver 1993 October 4-8

## 4aUW1. Internal waves and matched-field processing.

**Darrell R. Jackson
Terry E. Ewart
**

**
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*Appl. Phys. Lab., College of Ocean and Fishery Sci., Univ. of Washington,
Seattle, WA 98105
*

*
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The performance of matched-field processing is degraded due to randomness
of the propagation medium. With a vertical array, this degradation takes the
form of fragmentation and wandering of the peaks (mainlobe and sidelobes) in
the range-depth ambiguity surface. The resulting errors in localization are
characterized in terms of the rms processor output. Simulations and theory
specialized to the cw Bartlett processor are used. First, the case of an ocean
waveguide with a quadratic average sound-speed profile and vertically
stationary sound-speed fluctuation statistics is examined. Next, approximations
are introduced so that a relatively simple analytic model can be abstracted
from the theory. This model is checked against Monte Carlo PE computations that
avoid some of the simplifying approximations. The simple model contains scaling
rules for processor performance as a function of frequency, array length, and
medium vertical correlation length. In general, the effects of internal waves
become more important as frequency increases, array length increases, medium
correlation length decreases, and range increases. The processor is predicted
to be most sensitive to internal-wave mismatch for sources that are in
convergence zones. Finally, the analytical model is compared to Monte Carlo PE
computations using oceanic realizations obtained from a realistic dynamic
internal wave model.