The synergistic use of Landsat-8 Operational Land 1 Imager (OLI) and Sentinel-2 Multispectral Instrument (MSI) 2 data products provides an excellent opportunity to monitor 3 the dynamics of aquatic ecosystems. However, the merging of 4 data products from multi-sensors is often adversely affected 5 by the difference in their spectral characteristics. In addition, 6 the errors in the atmospheric correction (AC) methods further 7 increase the inconsistencies in downstream products. This work 8 proposes an improved spectral harmonization method for OLI 9 and MSI-derived remote sensing reflectance (R r s ) products, 10 which significantly reduces uncertainties compared to those 11 in the literature. We compared the R r s retrieved via state-12 of-the-art AC processors, i.e., Acolite, C2RCC, and Polymer, 13 against ship-based in-situ R r s observations obtained from the 14 Barents Sea waters, including a wide range of optical properties. 15 Results suggest that the Acolite-derived R r s has a minimum bias 16 for our study area with median absolute percent difference 17 (MAPD) varying from 9 to 25% in the blue-green bands. 18 To spectrally merge OLI and MSI, we develop and apply a 19 new machine learning-based bandpass adjustment (BA) model 20 to near-simultaneous OLI and MSI images acquired in the 21 years from 2018 to 2020. Compared to a conventional linear 22 adjustment, we demonstrate that the spectral difference is 23 significantly reduced from ∼6 to 12% to ∼2 to < 10% in the 24 common OLI-MSI bands using the proposed BA model. The 25 findings of this study are useful for the combined use of OLI 26 and MSI R r s products for water quality monitoring applications.
27The proposed method has the potential to be applied to other 28 waters.