Nonlinear internal waves in the South China Sea: Observation of the conversion of depression internal waves to elevation internal waves

The conversion of depression nonlinear internal solitons to elevation internal waves has been observed twice at the South China Sea continental shelf break. Shipboard X-band radar, tow-yo CTD, ADCP and high frequency acoustic flow visualization of the process are presented. The data focuses on up slope propagation of depression internal solitons from a water depth of similar to264 m to a water depth of similar to110 m. Dissipation by large amplitude shear instabilities was observed. The kinetic energy density was found to be a decreasing monotonic function of range with an energy dissipation rate coefficient of 0.063 km(-1). The rate of energy dissipation over the similar to16.5 km soliton propagation path was 0.17 W/m/m. Simple numerical models of the waveform evolution are qualitatively compared to the observations. The observations, extracted scale parameters and dissipation rates should be useful for testing a variety of evolution equation representations of internal soliton propagation.