Evaluation of the Geostationary Ocean Color Imager (GOCI) to monitor the dynamic characteristics of suspension sediment in Taihu Lake

Abstract

To accurately observe the dynamic concentration of total suspended matter (CTSM) by geostationary satellite, Geostationary Ocean Color Imager (GOCI), a new, regionally empirical combination algorithm, was developed based on the in situ measurement of water properties. Also, the ability of GOCI (with a 1 h temporal resolution) to capture dynamic change in CTSM was evaluated using in situ buoy-measured data. The validation results indicate that the combination algorithm (combination of two- and three-band ratio algorithms) can achieve acceptable retrieval results for CTSM, with 34.52% root mean square error percentage (RMSP) for validation data and 45.01% RMSP for GOCI match-up points. The depth of reflectance valley at 680 nm (Rrs-depth,680) is considered as an index for deciding whether to utilize a two- (Rrs-depth,680 ≤ 0.005) or three-band (Rrs-depth,680 > 0.005) algorithm in the combination algorithm. This combination algorithm overcomes some shortcomings of two- and three-band ratio algorithms of CTSM in turbid productive water. The results show that sediment resuspension will significantly change the optical properties of water and decrease the universality of the CTSM retrieval algorithm in the presence of a large area of algae. The influence of sediment resuspension on the CTSM retrieval algorithm is significant in the central lake but less so in the other four lakes studied due to lake morphology and algal biomass.