Validation of S3-OLCI Water Reflectance derived from Standard, C2RCC, BLR and DSF Processors in Complex Turbid Waters of Río de la Plata (Argentina)

DOGLIOTTI, A.I.; GOSSN, J.I

Encuentro; 5th Sentinel-3 Validation Team Meeting; 2019

Highlyturbid waters represent a challenge to atmospheric correction algorithms and thusfield measurements are critical to asses and improve their performance. Inparticular, the Río de la Plata is a large-scale and shallow funnel-shapeestuary which carries a large amount of suspended particulate and dissolved organicrepresenting an ideal scenario to test atmospheric correction algorithmsperformance. A match-up analysis has been performed using field measurementscollected in January 2017, April 2018 and November 2018 from the Fishermen Pierin Buenos Aires, the location where one of the HYPERNETS hyperspectralradiometer for automated measurements will be placed. Measurements of waterreflectance using a Trios/RAMSES radiometer and turbidity (portable HACH andin-water OBS501 sensor) have been collected coincidentally with Sentinel-3Aoverpasses. Field measurements have been compared to satellite-derived waterreflectance using three processors: 1) the ESA standard atmospheric correction (BAC/BPAC)that combines the base line (Antoine and Morel, 1999) and the bright pixelatmospheric correction (Moore et al. 1999), 2) the Case 2 Regional Coast Colour(C2RCC) based on neural networks (Brockman et al. 2016), and 3) the base lineresidual approach (BLR) that uses three spectrally-close band triplets to calculatewater reflectance at the red, NIR and SWIR OLCI bands (Gossnet al. 2019). For the Red and NIR bands (620, 709, 779 and 865nm), BLRprocessor showed better results, followed by the standard BAC/BPAC processor,while the C2RCC generally tended to underestimate measured values at theselonger wavelengths. In turn, C2RCC gives better results at shorter wavelengths(< 620 nm), while BAC/BPAC tended to underestimate field measurements, evenretrieving negative values in the blue bands (400, 412, and 442 nm).