Improving the Atmospheric Correction of OLCI over Turbid Waters by Using the SWIR band at 1016 nm and a new Baseline Residual Technique
Proceeding of Ocean Optics XXIV Conference. Dubrovnik, Croacia. 8 – 12 Oct., 2018.
Since April 2016, the OLCI era has begun, providing a new opportunity for atmospheric correction of turbid waters due to its novel spectral band in the SWIR. This new band at 1016 nm, which is much less expensive for the mission than longer SWIR bands (such as MODIS’ 1240, 1640 and 2130 nm bands) may give similar and even better performances than far-SWIR NIR bands for turbid water atmospheric correction with suitable algorithm development. Although water absorption at this band is 6.9 and 11.8 times higher than at 865 and 779 NIR bands, it is still not enough to fully absorb the backscattered signal produced by suspended sediments in very turbid waters such as Río de la Plata (Argentina). This means that alternative to the “black water” approach is needed for this sensor in this region which makspecial use of the new SWIR band. In this work, we present an atmospheric correction turbid waters developed for OLCI, based on Baseline Residuals (BLRs), i.e. spectral quantities computed from band triplets (in the same way as the Fluorescence Line Height algorithm) Rayleigh-corrected reflectances in the Red/NIR/SWIR bands. The BLR algorithm is evaluated compared to results obtained with standard atmospheric correction approaches, showing better general performance and spatial de-correlation between atmospheric and water signal. Although the algorithm has proven to yield satisfactory match ups of Total Suspended Matter (Delgado et al. [Ocean Optics XXIV, (2018)]), future efforts will be put in validating water reflectance using radiometric field measurements.