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Characteristics and generation of internal waves (IWs) in the Sulu Sea are studied using Moderate-Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) images taken from October 2016 to September 2019. Satellite observations show that IWs in the Sulu Sea mainly located in the shallower western areas with occasional observations in the deeper eastern regions. The dominant length of wave crest (LWC) of IWs is between 50 and 150 km with the largest LWC reaching over 300 km. The analysis of temporal distributions of IWs shows that March has the most IWs and July has the least. Further analysis shows that the seasonal variation is mainly due to the cloud contamination of optical satellite images. New generation sites of IWs are analyzed using satellite images. Six possible generation sites for IWs in the western Sulu Sea and one generation site for IWs in the eastern Sulu Sea are found using the ray-tracing method. Multi IW sources in the same strait are found, which may be due to the seawater fl ow over the strait in diff erent directions. The analysis shows that IWs with long wave crest in the Sulu Sea is a combined eff ort of all straits between small islands in the Sulu Archipelago. Remote generated IWs with long wave crest in the eastern Sulu Sea are studied, which are generated at the straits around (121.5°E, 6°N) by the nonlinear evolution of internal tide originated from the Sulu Archipelago. [ABSTRACT FROM AUTHOR]

The 20 Hz high sampling radar altimetry data and quasi-synchronous satellite images are applied to investigate internal waves in the South China Sea (SCS) and the Sulu Sea. The response characteristics and band sensitivities of radar altimetry data to the modulation of internal waves were analysed. With quasi-synchronous observations, the responses of Sigma0 and significant wave height (SWH) in the Ku band and the C band to the modulation were discussed, respectively. The results demonstrate that for Sigma0, the Ku band is more sensitive, whereas the C band is more sensitive for SWH. The propagation speeds of internal waves in the SCS and the Sulu Sea were calculated with quasi-synchronous observation of radar altimetry high sampling data and MODIS images. The calculated speed of the internal waves is close to the phase speed obtained from the KdV equation. This work indicates that the quantitative parameter of internal waves could be extracted from radar altimetry high sampling data. The altimetry data could serve as an additional data source for the investigation of internal waves. [ABSTRACT FROM AUTHOR]