Acoustic scattering from ocean microstructure

摘要: An examination is made of the scattering cross section per unit volume solid angle, σ, for case acoustic from ocean microstructure. Both monostatic and bistatic source/receiver geometries are considered. Diffraction explicitly included in formulation, resulting an expression σ which accounts finite effects associated with vertically anisotropic Vertically microstructure results a maximum at reflection respect to horizontal plane, where = σr, angular bandwidth order β0, α, β0 beamwidth angle volume, α anisotropy slope angle. For stratified part column, neglecting doubly diffusive effects, under typical open conditions, temperature induced dominates that fluid velocity by several orders magnitude. Two models microstructure, termed classical turbulence model empirical model, latter based on field observations, used as input into formulation. Specific functional forms obtained σr terms environmental parameters. frequencies 100 kHz greater, principally result wave number regimes corresponding inertial or Batchelor subranges. Typical modeled isotropic backscattering strengths Sv 10 log (σr) ≈ −110 dB. However, very narrow sonar systems, scales −20 angles internal waves would 37-dB increase strength. Intense high vertical shear zones such present Stellwagen bank Massachusetts Bay Knight Inlet, British Columbia, can −60 Bistatic particularly near-forward directions, general, greatly enhanced strength over backscattering.