Abstract
The Sentinel-3A satellite was launched on 16 February 2016 with the Ocean and Land Colour Instrument (OLCI-A) on-board for the study of ocean color. The accuracy of ocean color parameters depends on the atmospheric correction algorithm (AC). This processing consists of removing the contribution of the atmosphere from the total measured signal by the remote sensor at the top of the atmosphere. Five ACs: the baseline AC, the Case 2 regional coast color neural network AC, its alternative version, the Polymer AC, and the standard NASA AC, are inter-compared over two bio-optical contrasted French coastal waters. The retrieved water-leaving reflectances are compared with in situ ocean color radiometric measurements collected using an ASD FielSpec4 spectrometer. Statistical and spectral analysis were performed to assess the best-performing AC through individual (relative error (RE) at 412 nm ranging between 23.43 and 57.31%; root mean squared error (RMSE) at 412 nm ranging between 0.0077 and 0.0188) and common (RE(412 nm) = 24.15–50.07%; RMSE(412 nm) = 0.0081–0.0132) match-ups. The results suggest that the most efficient schemes are the alternative version of the Case 2 regional coast color neural network AC with RE(412 nm) = 33.52% and RMSE(412 nm) = 0.0101 for the individual and Polymer with RE(412 nm) = 24.15% and RMSE(412 nm) = 0.0081 for the common ACs match-ups. Sensitivity studies were performed to assess the limitations of the AC, and the errors of retrievals showed no trends when compared to the turbidity and CDOM.
Highlights
They represent only 7% of the total ocean surface, coastal and inland water zones produce up to 40% of the marine and freshwater biomass inventoried today and 85% of the marine and freshwater resources exploited by humans
On-board, two sensors are of interest for the monitoring of natural water bio-optical properties and surface temperature [13]: the Ocean and Land Colour Instrument (OLCI-A thereafter) [14] and the Sea and Land Surface Temperature Radiometer (SLSTR) [15]
A shorter time window can lead to better results in terms of Stot (BlAC, C2R-CC, and NASA for the individual match-ups)
Summary
They represent only 7% of the total ocean surface, coastal and inland water zones produce up to 40% of the marine and freshwater biomass inventoried today and 85% of the marine and freshwater resources exploited by humans. The European Space Agency (ESA) has developed an ambitious program called “Copernicus” whose aim is to provide continuous observations of the ocean and land for the twenty years through a series of Sentinel satellites. Among those Sentinel satellites are the Sentinel-3A and Sentinel-3B satellites [13], which were successfully launched on 16 February 2016 and 25 April 2018, respectively. On-board, two sensors are of interest for the monitoring of natural water bio-optical properties and surface temperature [13]: the Ocean and Land Colour Instrument (OLCI-A thereafter) [14] and the Sea and Land Surface Temperature Radiometer (SLSTR) [15]
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