Analytical and observational studies of internal solitary waves in the yellow sea

This article presents findings regarding the origination and evolution of a large train of internal solitary waves as observed through Synthetic Aperture Radar (SAR). The internal wave train under study propagates into deeper waters away from the coast and, most important, appears to be generated at a well-defined point along a steep topographic variation. The shallow bottom topography revealed itself in the SAR image and provided the opportunity to determine, with a large level of accuracy, the precise area where an internal bore originated. The bore traveled east and broke up into a train of solitary waves. The packet's phase speed, wave amplitude, mixed-layer depth, and density difference for a two-layer structure were remotely estimated based on measurements made from the SAR image, the knowledge of the local bathymetry, historical climatological data, and a two-layer model. Farther along the propagation path the internal waves exhibited an extremely large degree of dispersion, which was related to changing stratification conditions along the travel direction that are probably a consequence of the seasonal intrusion into the region of the low salinity plume of the Yangtze River. Monitoring changes in the dispersion characteristics of a soliton train from one tidal period to the next could, therefore, render remote information regarding changing stratification conditions in the area. This particularly long train of internal waves consisted of seven packets that traveled for three days along a well-defined direction. A new analytical model, termed the Dnoidal model, was used to describe the development of the internal waves with time. The extended life of this phenomenon provided an exceptional opportunity to monitor and model its evolution as well as to assess the effects of dispersion as the solitary internal waves propagated east, away from the China coast.