title: Low-frequency pulse propagation over 510 km in the Philippine Sea: A comparison of observed and theoretical pulse spreading.
abstract: Observations of the spread of wander-corrected averaged pulses propagated over 510 km for 54 h in the Philippine Sea are compared to Monte Carlo predictions using a parabolic equation and path-integral predictions. Two simultaneous m-sequence signals are used, one centered at 200 Hz, the other at 300 Hz; both have a bandwidth of 50 Hz. The internal wave field is estimated at slightly less than unity Garrett-Munk strength. The observed spreads in all the early ray-like arrivals are very small, <1 ms (for pulse widths of 17 and 14 ms), which are on the order of the sampling period. Monte Carlo predictions show similar very small spreads. Pulse spread is one consequence of scattering, which is assumed to occur primarily at upper ocean depths where scattering processes are strongest and upward propagating rays refract downward. If scattering effects in early ray-like arrivals accumulate with increasing upper turning points, spread might show a similar dependence. Real and simulation results show no such dependence. Path-integral theory prediction of spread is accurate for the earliest ray-like arrivals, but appears to be increasingly biased high for later ray-like arrivals, which have more upper turning points.
authors.affiliation: Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA.
authors.forename: Rex K
authors.initials: RK
authors.lastname: Andrew
authors.affiliation: Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Ganse
authors.affiliation: Marine Acoustics, Inc., Middletown, Rhode Island 02842, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: White
authors.affiliation: Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Mercer
authors.affiliation: Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Dzieciuch
authors.affiliation: Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Worcester
authors.affiliation: Department of Oceanography, Naval Postgraduate School, Monterey, California 93943, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Colosi