Ocean Variability & Acoustic Propagation

ISBN-13: 9789401054621 / Angielski / Miękka / 2012 / 608 str.

J. Potter; A. Warn-Varnas

Opis

Fifteen years ago NATO organised a conference entitled 'Ocean Acoustic Modelling'. Many of its participants were again present at this variability workshop. One such participant. in concluding his 1975 paper, quoted the following from a 1972 literature survey: ' ... history presents a sad lack of communications between acousticians and oceanographers' Have we done any better in the last 15 years? We believe so, but only moderately. There is still a massive underdeveloped potential for acousticians and oceanographers to make significant progress together. Currently, the two camps talk together insufficiently even to avoid simple misun derstandings. such as those in Table 1. Table 1 Ocsanographic and acoustic jargon (from an idea by Pol/ardi Jargon Oceanographic use Acoustic use dbordB decibar (depth in m) decibel (energy level) PE primitive equations parabolic equations convergence zone converging currents converging rays (downwelling water) (high energy density) front thermohaline front wave, ray or time front speed water current speed sound propagation speed 1 The list goes on."

Spis treści

Session 1 Experimental results relating acoustic and oceanographic variability.- Deterministic-stochastic oceanographic descriptions for ocean-acoustic experiments.- Experimental ocean acoustic field moments versus predictions.- Two dimensional acoustical propagation in a stratified shear flow.- The effects of sound speed on the shape of the ocean impulse response.- The effect of seasonal temperature fluctuations in the water column on sediment compressional wave speed profiles in shallow water.- SLICE89: A single slice tomography experiment.- Marginal Ice Zone oceanographic variability and its effects on acoustic propagation.- Internal wave induced fluctuations in the oceanic density and sound speed fields.- Gyre-scale reciprocal acoustic transmissions.- Summary of Session 1.- Session 2 Wave motion and finestructure affecting acoustic propagation: smallscale variability.- Chaos in underwater acoustics.- Impulse response analysis of ocean acoustic propagation.- Dependence of near-surface acoustic scatter on wind speed.- Nonlinear effects in wind-wave generation.- Multichannel acoustic reflection profiling of ocean watermass temperature/salinity interfaces.- Acoustic variability due to internal waves and surface waves in shallow water.- Observations of ocean inhomogeneities.- The problem of creating a synthetic aperture in a non-isotropic ocean.- Prediction of coastal ocean thermal variability.- Summary of Session 2.- Session 5 Stochastic modelling in oceanography and acoustics.- Treatments of incoherent scattering for the parabolic equation and ASTRAL propagation models.- Average sound intensities in randomly varying sound-speed structures.- Stochastic ray tracing in thermoclines.- Modeling of sound propagation in a randomly varying ocean by stochastic mode coupling.- Summary of Session 5.- Session 3 Range-dependent acoustic propagation caused by fronts and eddies: mesoscale variability.- Radar altimetry and acoustic prediction.- A range-dependent analysis of acoustic transmission across a cold filament in the California current.- Acoustic effects of the Iceland—Faeroe front.- Deep hydrographic fluctuations in the north-east Atlantic Mediterranean outflow: influence on acoustic propagation.- Aspects of oceanographic variability observed from thermistor chains on free-drifting buoys.- Theoretical determination of the fractal dimension of fluid parcel trajectories in large and meso-scale flows.- How do eddies modify the stratification of the thermocline?.- Three-dimensional oceanography and acoustics.- Frontal boundaries and eddies on the Iceland—Faeroes ridge.- Upper ocean variability associated with fronts.- Summary of Session 3.- Session 4 Coupling acoustic and oceanographic models.- A mixed-layer model for predicting the acoustic structure of shallow seas.- The use of coupled ocean-acoustic models in the design of naval forecast systems.- The Environmental Acoustic Tactical Support System: low frequency mesoscale ocean feature environmental acoustic results.- Environmental focusing and source localization in the ocean.- Refraction of acoustic modes in very long-range transmissions.- Environmental sensitivity studies with an interfaced ocean-acoustics system.- Simulating temperature, salinity and currents in the ocean.- A numerical investigation of semi-diurnal fluctuations in acoustic intensity at a shelf edge.- Summary of Session 4.- List of Participants.- Author Index.