Satellite Estimates of Wide-Range Suspended Sediment Concentrations in Changjiang (Yangtze) Estuary Using MERIS Data
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The Changjiang (Yangtze) estuarine and coastal waters are characterized by suspended sediments over a wide range of concentrations from 20 to 2,500 mg l−1. Suspended sediment plays important roles in the estuarine and coastal system and environment. Previous algorithms for satellite estimates of suspended sediment concentration (SSC) showed a great limitation in that only low to moderate concentrations (up to 50 mg l−1) could be reliably estimated. In this study, we developed a semi-empirical radiative transfer (SERT) model with physically based empirical coefficients to estimate SSC from MERIS data over turbid waters with a much wider range of SSC. The model was based on the Kubelka–Munk two-stream approximation of radiative transfer theory and calibrated using datasets from in situ measurements and outdoor controlled tank experiments. The results show that the sensitivity and saturation level of remote-sensing reflectance to SSC are dependent on wavelengths and SSC levels. Therefore, the SERT model, coupled with a multi-conditional algorithm scheme adapted to satellite retrieval of wide-range SSC, was proposed. Results suggest that this method is more effective and accurate in the estimation of SSC over turbid waters.
KeywordsMERIS data Semi-empirical radiative transfer model Suspended sediment concentration Turbid waters Changjiang estuary
This research was funded by National Natural Science Foundation of China (no. 40871165) and the “111 Project” (B08022). Field data were supported by the Creative Research Groups of China from the NSFC (no. 40721004) and the “973 National Basic Research Program.” The authors are grateful to scientists and graduate students from our laboratory for their assistance in in situ measurements and samplings. Thanks to the European Space Agency (ESA) for providing MERIS data via the support of ESA approved Cat-1 project (id. 4359). We are grateful to three anonymous reviewers and editors for their helpful comments and suggestions.
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