Study on the amplitude inversion of internal waves at Wenchang area of the South China Sea
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Study on the amplitude inversion of internal waves at Wenchang area of the South China Sea ZHANG Xudong1, WANG Jing1, SUN Lina2, MENG Junmin2* 1 College of Information and Engineering, Ocean University of China, Qingdao 266100, China 2 First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
Received 4 August 2015; accepted 22 January 2016 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2016
Abstract
The field experiment is conducted from April 16, 2005 to July 20, 2005 at Wenchang area east of Hainan Island (19°35'N, 112°E) of China. Internal wave packets are observed frequently with thermistor chains during the experiment. Meanwhile, internal waves are also detected from a synthetic aperture radar (SAR) image on June 19, 2005 and several other moderate-resolution imaging spectroradiometer (MODIS) images near a mooring position. The distance between the positive and negative peaks induced by the internal wave can be obtained from satellite images. Combined with remote sensing images and in situ data, a new method to inverse the amplitude of the internal wave is proposed based on a corrected nonlinear Schrödinger (NLS) equation. Two relationships are given between the peak-to-peak distance and the characteristic wavelength of the internal wave for different nonlinear and dispersion coefficients. Based on the satellite images, the amplitude inversion of the internal waves are carried out with the NLS equation as well as the KdV equation. The calculated amplitudes of the NLS equation are close to the observation amplitude which promise the NLS equation a reliable method. Key words: internal wave, amplitude inversion, nonlinear Schrödinger equation, remote sensing image, Wenchang area Citation: Zhang Xudong, Wang Jing, Sun Lina, Meng Junmin. 2016. Study on the amplitude inversion of internal waves at Wenchang area of the South China Sea. Acta Oceanologica Sinica, 35(7): 14–19, doi: 10.1007/s13131-016-0902-1
1 Introduction Internal waves with large amplitude will induce a strong underwater current and have a significant impact on offshore engineering, diapycnal mixing, military safety like submarine navigation and underwater acoustic propagation. Hence, the research on the amplitude of the internal waves is of great significance. The combination of in situ observation and satellite detection as well as numerical models has been reported to investigate the internal waves which all prove to be useful methods. The Asian Seas International Acoustic Experiment (ASIAEX) during 2000 and 2001 has obtained precious observation data, which deepened our understanding of the internal waves (Orr and Mignerey, 2003; Yang et al., 2004). Ramp et al. (2004) classified internal solitary waves as type-a and type-b waves based on the ASIAEX data in the South China Sea (SCS). Alford et al. (2010) have used the data across the SCS Basin to study the speed and structural change of the internal waves. Liu et al. (2013) have studied the generation and evolution of mode-two internal wave
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