The effect of mineral sediments on satellite chlorophyll-a retrievals from line-height algorithms us

Session: Remote Sensing, Visualization, and Spatial Data Applications for the Great Lakes (1)

Caren Binding, Environment Canada, [email protected]
Chuiqing Zeng, Environment and Climate Change Canada, [email protected]

Abstract

Red and near-infrared line-height algorithms such as the Maximum Chlorophyll Index (MCI), Cyanobacteria Index (CI) and Maximum Peak Height (MPH) are often considered optimal for remote sensing of Chlorophyll-a (Chl-a) in eutrophic waters under the assumption of minimal influence of coloured dissolved organic matter (CDOM) and robustness to atmospheric correction challenges over turbid inland waters. These algorithms are also assumed to be fairly insensitive to mineral sediments and as such are often applied to waters prone to high sediment loads from river inputs, resuspension events or shoreline erosion. This study applies radiative transfer simulations to investigate the impact of mineral turbidity on these algorithms. Simulated spectra confirm a non-linear relationship between Chl-a and MCI, suggesting optimal use of the MCI at Chl-a < ~100 mg/L and saturation of the index at Chl-a ~300 mg/L. Results suggest significant enhancement of the MCI signal from mineral scattering with increasing Chl-a leading to increased uncertainty in chlorophyll retrievals. Mineral sediments are also shown to have a measureable effect on the baseline slope of the MCI, which forms the basis of a novel approach for reducing uncertainties in MCI-derived Chl-a in turbid waters