title: The effect of wind-generated bubbles on sea-surface backscattering at 940 Hz.
abstract: Reliable predictions of sea-surface backscattering strength are required for sonar performance modeling. These are, however, difficult to obtain as measurements of sea-surface backscattering are not available at small grazing angles relevant to low-frequency active sonar (1-3 kHz). Accurate theoretical predictions of scattering strength require a good understanding of physical mechanisms giving rise to the scattering and the relative importance of these. In this paper, scattering from individual resonant bubbles is introduced as a potential mechanism and a scattering model is derived that incorporates the contribution from these together with that of rough surface scattering. The model results are fitted to Critical Sea Test (CST) measurements at a frequency of 940 Hz, treating the number of large bubbles, parameterized through the spectral slope of the size spectrum for bubbles whose radii exceed 1 mm, as a free parameter. This procedure illustrates that the CST data can be explained by scattering from a small number of large resonant bubbles, indicating that these provide an alternative mechanism to that of scattering from bubble clouds.
authors.affiliation: TNO, Oude Waalsdorperweg 63, P.O. Box 96864, 2509 JG The Hague, The Netherlands. robbert.vanvossen@tno.nl
authors.forename: Robbert
authors.initials: R
authors.lastname: van Vossen
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ainslie
mesh_terms: D000042:Absorption; D008962:Models, Theoretical; D009038:Motion; D009792:Oceans and Seas; D010316:Particle Size; D012542:Scattering, Radiation; D013016:Sound; D013499:Surface Properties; D013997:Time Factors; D014465:Ultrasonics; D014867:Water; D014919:Wind
chemical_list: D014867:Water