ABSTRACTS

Oral Session 11 | Friday, October 7, 10:00–10:20 | Abstract 583

Atmospheric correction for diverse optical water types

We introduce A4O, a novel method for atmospheric correction of Sentinel-3 OLCI ocean colour imagery intended to work for all Optical Water Types (OWT) that represent inland, coastal and ocean waters. The method is an extensive revision of the C2RCC processor, that is implemented in the Sentinel Application Platform (SNAP) and which has been selected by ESA as atmospheric correction branch for optically complex waters in the Sentinel-3 OLCI ground segment processor. The core of A4O is an ensemble of several neural networks that approximate fully-normalized remote-sensing reflectance at 16 OLCI bands from the top-of-standard-atmosphere reflectance spectrum. Special emphasis is placed on high classifiability of R rs with an OWT framework for selecting and blending retrievals from water type-optimized water algorithms, i.e. the spectral shape of R rs is essential. In comparison with other atmospheric corrections, the novel method shows significant advantages: 1) the scope of applicability of A4O includes all OWTs that are usually considered, 2) A4O delivers optically plausible R rs shapes even in cases with intense algae blooms, extremely turbid (scattering) waters, and cases with significant absorption by coloured dissolved organic matter 3) A4O delivers reflectances that are mostly well OWT-classifiable, 5) spatial noise is reduced. The general performance of A4O is illustrated by means of optically diverse satellite images. Validation is performed by comparison of OLCI match-ups with spectral in-situ data from the Aeronet-OC network and measurements from own campaigns. 

Martin Hieronymi, Helmholtz-Zentrum Hereon, 0000-0001-6066-1562

Shun Bi, Helmholtz-Zentrum Hereon

Eike Schütt, Helmholtz-Zentrum Hereon

Dagmar Müller, Brockmann Consult