Retrieval and Analysis of Sea Surface Salinity in the Adjacent Waters of the Yangtze River Estuary Based on Multisource Satellite Data

Cao, K.; Sun, W.; Chen, L.; Meng, J., and Zhang, J., 2020. Retrieval and analysis of sea surface salinity in the adjacent waters of the Yangtze River Estuary based on multisource satellite data. Journal of Coastal Research, 36(3), 590–599. Coconut Creek (Florida), ISSN 0749-0208.Moderate Resolution Imaging Spectroradiometer, Sea-Viewing Wide Field-of-View Sensor, and Visible Infrared Imaging Radiometer Suite multisource satellite remote sensing reflectance data are used with in situ sea surface salinity (SSS) measurements in the Yellow Sea and East China Sea. A linear algorithm is developed for the retrieval of summer SSS in adjacent waters of the Yangtze Estuary in the Yellow Sea and East China Sea. The accuracy of SSS retrieval results is validated using independent in situ measurements. Results show that the mean bias of the model is –0.34 psu, the root-mean-square error is 1.55 psu, and the correlation coefficient is 0.80. The linear model is extended to the retrieval of multisource satellite monthly remote sensing reflectance data to obtain monthly SSS products of the Yangtze Estuary. The spatial coverage of fused satellite SSS data is about 10% greater than that of single-satellite monthly retrieved SSS data. The SSS in the Yangtze Estuary research area has lower values nearshore and higher values offshore. The SSS gradually rises from nearshore areas to open water, and an obvious low-salinity water tongue forms in the Yangtze Estuary. The eastward expansion of freshwater flows of the Yangtze River into the sea is mainly affected by the runoff of the Yangtze River, while a southerly wind and northeastward flow in the research area are the main factors responsible for the eastward expansion of the Yangtze River freshwater flows to the NE. The effect of freshwater on the Yellow Sea and East China Sea extends to 125.5° E, and the low-salinity freshwater tongue distributes northeastward. The expansion types of the Yangtze River freshwater include NE expansion, N-NE expansion, E-NE expansion, bidirectional expansion, and nondirectional expansion.