Predictive Parametric Model for Volume Scattering Strength in the Deep Ocean with an Application to Nighttime Near-Surface Scattering in the North Sargasso Sea Below 16 kHz.

摘要

In the deep ocean, long range active sonars are often volume reverberation limited at night due to scattering from the gas-filled swimbladders of mesopelagic fish in near-surface waters. To predict the detection performance of these sonars with a general sonar model, volume scattering strength profiles Sv(z,f) are needed as inputs. A general volume scattering strength model (VSSM) for nighttime/daytime Sv(z,f) profiles in a deep water faunal province is described. Explicit expressions are developed tor the average length-depth distribution of bladdered fish, the corresponding swimbladder radius-depth distribution, and volume scattering strength Sv(z,f). A specific nighttime near-surface VSSM is developed for the North Sargasso Sea faunal province using data from Ocean Acre experiment 12. A VSSM of very simple form is found capable of describing measured nighttime profiles at 3.85 and 15.5 kHz to a depth of 225 m. This agreement, however, could only be obtained by modifying model parameters obtained from trawl data to correct for sampling deficiencies, principally net avoidance by the larger fish. Predictions with the modified VSSM at 1 kHz suggest that in the nighttime 0-50 m surface layer, Sv-levels were as high as -75 dB due to scattering from these larger fish. Volume scattering strength model, Ocean Acre scattering layers, Swimbladder target strength, Bioacoustic volume scattering model, Mesopelagic bladdered fish scatterers, Swimbladder Q-factor.