Systematic studies of pulse propagation in ducted oceanic waveguides in normal mode representation

Physics Department, University of Louisiana at Lafayette, USA

Corresponding author: nsidorovskaia@louisiana.edu

Received: 24 February 2003
Revised: 5 September 2003
Accepted: 20 October 2003
Published online: 22 December 2003

Abstract

Acoustic pulse propagations in typical environments of the Gulf of Mexico and Yellow Sea are modeled by a new normal mode code, SWAMP, and compared to the experimental data. The presence of the seasonal surface duct in the ocean is confirmed to be responsible for the generation of a unique set of modes forming the so-called “Precursor Phenomenon” first discovered by DeFerrari and Monjo. It is shown that the conventional theory of group velocity fails to predict precursor's arrival time. Two different approaches, the mean rate of energy transport and Airy-wave analysis, are proposed for the description of the actual physical process of energy transport by precursors. The influence of the range-dependent bathymetry on a precursor structure is addressed. The presence of precursors appears to be sensitive to range dependence and may be diminished due to rapidly changing bathymetry. Based on numerical results, inversion procedures of extracting different environmental and source parameters from a received pulse structure are discussed.