Effects on acoustics caused by ocean solitons, Part B: Acoustics

摘要

Large amplitude internal solitary waves in the ocean can interfere with underwater acous- tic signals. For certain acoustic parameters (source depth, receiver depth, and frequency) a redistribution of acoustical energy to higher-order acoustic modes can occur as the acoustic signal propagates through the solitary wave train. Depending on the ocean bottom compo- sition, this can result in a significant loss in acoustical signal intensity. In order to simulate and understand this phenomena, it is necessary to generate a solitary wave train that is realistic and contains the spectral components that will interact with the acoustic signal. This requires a primitive equation nonhydrostatic ocean model. Part A [A.C. Warn-Varnas, S.A. Chin-Bing, D. King, J. Hawkins, K. Lamb, Effects on acoustics caused by ocean solitons: Part A. Oceanography, Nonlinear Anal., in press (doi:10.1016/j.na.2009.02.104)] of this two- part article addressed that issue. In this work we use acoustic model simulations to demon- strate the mode linkage between the solitary wave train and the acoustic signal that can result in a large signal loss. Understanding the linkage allows for pre-examination of the solitary wave characteristics to determine if they could affect propagating acoustic signals. The procedure has the advantage that only a few computer runs are required from the ocean model and no lengthy computer runs are required from acoustic propagation mod- els. Only a quick calculation of the acoustic mode eigenvalues is needed.