Current field features and propagation characteristics of suspected internal solitary wave packet

The observational data of acoustic Doppler current profiler (ADCP) indicates that a suspected internal solitary wave packet (ISWP) consists of two depression waves in the northern South China Sea (SCS). This paper analyzes the current field features and propagation characteristics of the front and rear waves, calculates their propagation phase speeds and direction angels respectively, and demonstrates that the generation site of the suspected ISWP is Luzon Strait (LS).The our result shows that for the front wave, the height is 96 m, the time period is 16 min, the propagation phase speed is 1.04 m s−1, the direction angel is 283.4°, and the wavelength is 1.0 km; for the rear wave, the height is 80 m, the time period is 14 min, the propagation phase speed is 0.89 m s−1, the direction angel is 299°, and the wavelength is 0.74 km. The maximum horizontal velocity of the front wave is 1.1 m s−1 in depth 106 m below the sea surface, and the maximum shear is 0.030 s−1 in the wave trough; the maximum horizontal velocity of the rear wave is 0.84 m s−1 at the same depth and the maximum shear is 0.020 s−1 in the wave trough as well. According to the data and theoretical analysis there is an interaction between the front and rear waves 17 km to the direction of LS, showing that they were not generated during the same time interval. In this paper, our results may provide understanding the physical features and propagation characteristics of sequential internal solitary waves and their relationships.