Satellite Estimates of Wide-Range Suspended Sediment Concentrations in Changjiang (Yangtze) Estuary Using MERIS Data

Abstract

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 multiconditional 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.

Fusion of Landsat-8/OLI and GOCI Data for Hourly Mapping of Suspended Particulate Matter at High Spatial Resolution: A Case Study in the Yangtze (Changjiang) Estuary

“…For the extremely turbid waters in the Yangtze estuary, Pan et al [35] proposed the Enhanced Spectral Optimization Algorithm (ESOA) based on a coupled aerosol-water model. The coupled model combines an Aerosol Robotic Network (AERONET)-based aerosol model and a simple semi-empirical radiative transfer (SERT) model [36]. The coupled model includes four unknown parameters: the relative humidity (RH), fine-mode fraction (FMF), AOD in the NIR wavelength τ a (865) and [SPM].…”

“…The SERT model builds the relationship between the remote sensing reflectance R rs and [SPM] based on a two-stream approximation radiative transfer model [36]. The forward form of SERT is as follows:…”

“…Radiometric measurements were recorded by the Hyperspectral Surface Acquisition System (HyperSAS, Satlantic Inc., Halifax, Nova Scotia, Canada) and consist of the sea-surface radiance (L t ), sky radiance (L i ) and solar irradiance (E s ) from 350 to 900 nm in 136 spectral channels. Details about the sensors' mounting and observation geometries can be found in Shen et al [36,39]. R rs was calculated by [40,41]:…”

“…where Considering the sensitivity of [SPM] to R rs at different wavelengths, Shen et al [36,39,44] proposed an inversion scheme based on band shifting for SPM retrieval from satellite imagery in the Yangtze estuary. In this study, we used the three-band shifting scheme for SPM retrieval from GOCI and L8/OLI data.…”

Potential of High Spatial and Temporal Ocean Color Satellite Data to Study the Dynamics of Suspended Particles in a Micro-Tidal River Plume

“…This saturation first occurs at short (blue, green) visible wavelengths then in the red spectral region (at about 10 and 50 g¨m´3 at 555 and 645 nm, respectively) [15,16,47] and even in the NIR for extremely high SPM concentrations [48]. Depending on the SPM concentration range, Rrs variations within green, red or NIR spectral bands may be more sensitive, hence appropriate for the retrieval of SPM concentration [14,15,49].…”