Correcting ocean colour reflectance for absorbing aerosols

Abstract

Absorbing aerosol artefacts are persistent in Sea‐viewing Wide Field‐of‐View Sensor (SeaWiFS) imagery. Atmospheric aerosols absorb light with a strong spectral bias toward shorter wavelengths. Failure to account for their effects can result in underestimates of satellite‐derived water reflectance and overestimates of satellite‐derived chlorophyll concentrations. In this paper, a method to estimate and remove part of this artefact is presented. The method assumes (1) the total artefact is the difference between the current satellite reflectance and true reflectance; and (2) the spectral shape of the artefact caused by absorbing aerosols can be approximated by λ−n , where λ is wavelength and n = 6. The solution is explained using an in‐water bio‐optical model but is solved separately using the scattering characteristics of the atmosphere. An error analysis with variable amounts and different spectral types of aerosol artefact indicates that the method adjusts for absorbing aerosol with increasing frequency as the magnitude of the artefact increases. The correction shows robustness to different quantities of aerosol artefacts.