Acoustic scintillation due to shallow-water internal solitary waves: Theory and experiment

In August–September 1990, an acoustics experiment was performed in the shallow-water region near Kamchatka. A 11/2-h time series representing amplitude fluctuations of 800-Hz, 160-Hz-bandwidth acoustic pulses was obtained by a hydrophone moored 34 km from the source. During the same period, a time series representing solitonlike vertical displacements of the thermocline near the receiver was recorded using a 37.5-m vertical temperature sensor. The two records were found to display abnormal similarity at time delays of 16.5 and 44.5 min. The effect is shown to be due to modal synchronism that may take place in shallow-water lossy-bottom regions with a small downward-positive gradient of the sound velocity. Theoretical explanation is verified by numerical simulation in which received signals are modeled by Fourier synthesis based on coupled-mode wave-field solutions in a stratified channel with a moving internal solitary wave. On the basis of the theory developed, new possible approaches for acoustic remote sensing are discussed.