Spectral signature characters based on measurement in situ of high turbid water in Yangtze River estuary

Estimated total sediment mass in the fluid mud system is about 4.25×10⁸ tons per year as river inputs into Yangtze River estuary. The spatial-temporal distribution of suspended sediment concentration (SSC) is concerned by estuarine and coastal researchers. In this work, in situ measurements were carried out in Yangtze River estuary in Sep.2004, Jul. and Aug.2005 and Feb.2006. An experiment in barrel on land as a complementary measurement was conducted in July 2006. All of the spectral signatures observed show three spectrum-peak (at wavelengths 590nm, 690nm and 810nm around) characters more sensitive to SSC variation at bands 500-900nm. Remote sensing reflectance (Rrs) at 590nm around is bigger than that at 690nm around when SSC is about <0.1g/l, but this situation would be opposite when the SSC surpasses about 0.15g/l. The Rrs at 810nm around is lower than that respectively at 590nm and 690nm around, except that SSC increased to one close to or even > 1.0g/1. Here a parameter SRP (Sediment Response Parameter) described a changeable rate of ratios among three spectral peaks was defined, which presented a logarithmic decreasing tendency with the SSC increasing. The preliminary result shows that SRP can reflect SSC variation in the estuary.