title: Matched-field processing gain degradation caused by tidal flow over continental shelf bathymetry.
abstract: Temporally variable, range dependent sound-speed profiles measured during ebb flow and estimated for slack flow are used to quantify the variability of matched-field signal-processing gain degradation in shallow water propagation channels controlled by tidally driven stratified flow over variable bathymetry. Calculations along a 9.3 km range establish phase changes in the acoustic signal as the primary cause of a 3-9 dB degradation in the coherent matched-field processing output of a full water column vertical array. The work indicates that over a tidal cycle acoustic signal properties and matched-field processing gain can be expected to change continuously in a shallow water stratified channel that has bathymetry variability. Acoustic signals propagating in such tidal flow-controlled environments may be expected to display repeatable (over successive tidal cycles) and predictable changes in their phase coherent properties. These results suggest that matched-field processor replica fields used in the shelf/slope propagation environment will have to be updated regularly during a tidal cycle to maintain maximum processor gain.
authors.affiliation: Acoustics Division, Naval Research Laboratory, Washington, DC 20375-5320, USA.
authors.forename: Marshall H
authors.initials: MH
authors.lastname: Orr
authors.forename: Peter C
authors.initials: PC
authors.lastname: Mignerey