Internal solitary waves in the East China Sea

A European Space Agency’s ENVISAT advanced synthetic aperture radar(ASAR)image covering Zhejiang coastal water in the East China Sea(ECS)was acquired on 1 August 2007.This image shows that there are about 20 coherent internal solitary wave(ISW)packets propagating southwestward toward Zhejiang coast.These ISW packets are separated by about 10 km,suggesting that these ISWs are tide-generated waves.Each ISW packet contains 5-15 wave crests.The wavelengths of the wave crests within the ISW packets are about 300 m.The lengths of the leading wave crests are about 50 km.The ISW amplitude is estimated from solving KdV equation in an ideal two-layer ocean model.It is found that the ISW amplitudes is about 8 m.Further analysis of the ASAR image and ocean stratification profiles show that the observed ISWs are depression waves.Analyzing the tidal current finds that these waves are locally generated.The wavelength and amplitude of the ECS ISW are much smaller than their counterparts in the South China Sea(SCS).The propagation speed of the ECS ISW is also an order of magnitude smaller than that of the SCS ISW.The observed ISWs in the ECS happened during a spring tide period.