Densely-sampled internal wave data obtained from an experiment in the Yellow Sea are presented. Large amplitude, low-frequency internal waves with asymmetric waveforms are clearly seen in the strong seasonal thermocline. Deterministic and in particular statistical properties of these nonlinear internal tides are analyzed. It is found that their probability distributions are positively skewed and have higher peaks than the corresponding normal ones. The deviations from the normal are measured by the skewness and kurtosis coefficients.
Internal waves occur within marine subsurface layers that are stratified due to temperature and salinity gradients. These waves, at scales from a few hundred meters to tens of kilometers, have a significant role in the energy and mass transport within the ocean. They can influence offshore engineering operation, undersea navigation, and even biological productivity (Wang, 1999; Wang and Gao, 1999). Internal waves on the continental shelf have been extensively studied, and an overview has recently been given on remote sensing and in situ observations of internal tides, solitary waves and bores in shallow water by Wang and Gao (2000a). Longwavelength solitary waves of height as large as 8m were observed during the 1984 SAR internal wave signature experiment conducted in the New York Bight (Gasparovic et al, 1988). The evolution of an internal tide was measured on the Australian North West Shelf in 1992. Solitons of approximately 40m height were observed between slope and shelf moorings. A numerical solution of the KdV equation, including horizontal variability and dissipation, was used to model the transformation of an initially sinusoidal long internal wave representing the internal tide (Holloway et al, 1997). A large-scale shallow-water internal wave acoustic scattering experiment was performed in the shelf region off the coast of New Jersey in 1995.
