A DETERMINISTIC APPROACH TO UNDERSTANDING THE SENSITIVITY OF SURFACE DUCT PROPAGATION TO SOUND SPEED FEATURES IN THE UPPER OCEAN
Zinicola-Lapin, William N.
Colosi, John A.
Reeder, Davis B.
MetadataShow full item record
A key sound speed feature of the upper ocean is the Mixed Layer Acoustic Duct (MLAD). Acoustic propagation effects due to mean properties of the duct and spatial and temporal variability are thought to be strong functions of acoustic frequency. Key physical mechanisms at work are diffractive leakage and mode coupling. Using both analytic theory and direct numerical simulation, this thesis will examine 400 and 1000 Hz MLAD propagation characteristics by calculating the sensitivity of duct propagation to various ocean perturbations with horizontal scales ranging from 0.5 to 15 km. As a starting point, sound speed profiles (SSP) typical of the spring-summer transition in the North Atlantic are considered. Tools used are first-order mode scattering theory originally developed for shallow water propagation, and direct numerical simulation. Numerical simulations are compared to theory with the goals of 1) evaluating the utility of the shallow water analytic approach for deep water MLADs and 2) putting forward a metric for estimating MLAD stability as a function of frequency and perturbation scales. Results show that while the shallow water analytic approach is not accurate enough for the MLAD due to higher order mode interaction, first-order mode energy equation motivates the non-dimensional interaction matrix, Γmn, which showed strong correlation between multiple scattering events and increased acoustic variability when Γmn > 1.
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Showing items related by title, author, creator and subject.
Development of a labolatory facility for the measurement of sound propagation in shallow water environment Pongsitanont, Nakorn (Monterey, California. Naval Postgraduate School, 1989-12);The propagation of sound in a laboratory-modeled, shallow water environment consisting of water overlying a thick layer of water-saturated sand was experimentally investigated. A hydrophone consisting of a small lead-titanate ...
A smart climatology of evaporation duct height and surface radar propagation in the Indian Ocean Twigg, Katherine L. (Monterey, California. Naval Postgraduate School, 2007-09);Surface electromagnetic propagation over the ocean is highly sensitive to near-surface atmospheric variability, particularly the height of the evaporation duct. Seasonal variation in near-surface meterological factors and ...
An examination of higher-order treatments of boundary conditions in split-step Fourier parabolic equation models Erdim, Savas (Monterey, California: Naval Postgraduate School, 2015-06);Parabolic equation models solved using the split-step Fourier (SSF) algorithm, such as the Monterey Miami Parabolic Equation model, are commonly used to predict underwater sound propagation in deep and shallow water ...