Broadband acoustic signal variability induced by internal solitary waves and semidiurnal internal tides in the northeastern East China Sea

Jungyong Park; Woojae Seong; Haesang Yang; SungHyun Nam; Seung-Woo Lee; Youngmin Choo

doi:10.1121/1.5121715

Broadband acoustic signal variability induced by internal solitary waves and semidiurnal internal tides in the northeastern East China Sea

J Acoust Soc Am. 2019 Aug;146(2):1110. doi: 10.1121/1.5121715.

Authors

Jungyong Park¹, Woojae Seong², Haesang Yang², SungHyun Nam³, Seung-Woo Lee³, Youngmin Choo⁴

Affiliations

¹ Agency for Defense Development, Jinhae, P.O. Box 18, Changwon 51678, Gyeongsangnamdo, Korea.
² Department of Naval Architecture and Ocean Engineering/Research Institute of Marine Systems Engineering, Seoul National University, Seoul 08826, Korea.
³ School of Earth and Environment Sciences, Seoul National University, Seoul 08826, Korea.
⁴ Department of Defense System Engineering, Sejong University, Seoul 05006, Korea.

PMID: 31472556
DOI: 10.1121/1.5121715

Abstract

The relation between high-frequency broadband acoustic signal variability and two types of internal waves (short-period internal solitary waves; ISWs, and semidiurnal internal tides; ITs) is investigated using data collected during the shallow-water acoustic variability experiment 2015 in the northeastern East China Sea. In this flat (∼100 m depth) region, an underwater sound channel with sound speed profile (SSP) variability observed during the experiment significantly affects the acoustic variability induced by the ISW, and the arrival structure of the channel impulse response (CIR) modeled by ray tracing. To model the range-dependent SSP due to ISW, the location and characteristics of the mode-1 ISW of wavelength (0.5-1 km) are estimated and verified based on the two-layer Korteweq-de Vries theory and by analyzing the observed temperature fluctuations. It is found from comparison between the measured and modeled CIRs that the ISW scatters the arrival structures of refracted rays. Meanwhile, semidiurnal ITs change the channel size modeled as range-independent considering the wavelengths (15-40 km) longer than the model range (3 km). Higher centroid of acoustic arrival time is found with lower isotherm depressions owing to the multimode ITs, indicative of acoustic energy focusing at the lower channel region.