Low-frequency internal waves and their influence on transmission loss variability

P. Kumar (), A. Rao, K. Anilkumar, M. Padmanabham and K. Radhakrishnan

Natural Hazards: Journal of the International Society for the Prevention and Mitigation of Natural Hazards, 2011, vol. 57, issue 3, 643-656

Abstract: Analysis of the time series data collected from a stationary location in the continental shelf of the southeastern Arabian Sea during different month indicated prominent internal wave (IW) activity. Time evolution of temperature, resolved using Morlet wavelet technique, revealed that maximum energy was concentrated in the diurnal band at the density interface, whereas within the interior of thermocline, the dominant energy concentration shifted to semi-diurnal band. Both these harmonics have maximum amplitude (>15 m) during the pre-monsoon and monsoon season when the water column was highly stratified (>0.05 kg/m 4 ), but they were not discernable in the temperature record when the stratification was weak (i.e., especially during winter). An acoustic propagation model based on ray theory, Bellhop (http:/oalib.hlsresearch.com/modes/acoustictoolbox/at.zip) was utilized to compute the transmission loss (TL) associated with the passage of low-frequency IWs. The TL was computed using the model considering (1) range-dependent and range-independent environmental scenario and (2) for different source and receiver depth configurations. Intermittent fading of acoustic signals was observed in the presence of IW. It was also observed that fading of signals very much depends on the source–receiver configuration. Copyright Springer Science+Business Media B.V. 2011

Keywords: Internal waves; Southeastern Arabian Sea; Wavelet transform; Acoustic propagation model; Transmission loss (search for similar items in EconPapers)
Date: 2011
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DOI: 10.1007/s11069-010-9629-z

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