Development of a new algorithm of suspended sediment concentration from satellite remote sensing data in the East China Sea

Suspended sediment is an important parameter of water quality and a main factor to affect the lifetime of port use, which needs to be monitored on the spatial distribution and temporal changes. It also dominates the optical properties in the coastal ocean and makes it difficult to retrieve chlorophyll concentration and other water constituents from satellite remote sensing data. Many algorithms were developed to retrieve suspended sediment concentration (SSC) from satellite remote sensing data and most of them were tested to be used for the region of the East China Sea. The results show that relative errors are too large to be more than 100% under high concentration of sediments. This region, especially in the Yangtze estuary and Hangzhou Bay, is famous for large area distribution of high concentration of suspended sediment, as high as more than 1000 mg/l. A new algorithm is developed, based on a large amount of in-situ measurements of four big cruises, each of these cruises employ two big ships to take about two months to measure about 200 stations. First, the relationship between the water-leaving radiance at different wavelengths and SSC was analyzed and the results show that the radiance at green bands is sensible to SSC at low concentration and almost saturated at high concentration, while the radiance at red bands has a good relationship with SSC at high concentration, meanwhile the radiance at near-infrared bands has also a big value under high SSC. Then the accuracy of the algorithm is evaluated and shows that the algorithm has a nice performance both at low and high SSC. Finally, the algorithm is used to obtain SSC from SeaWiFS and MODIS data and the distribution of SSC show that the algorithm is suitable for retrieving SSC from satellite remote sensing data in the East China Sea.