The CoASTS-BiOMaP data set comprises in situ near-surface inherent (e.g., absorption, scattering and backscattering coefficient s) and apparent (e.g., normalized-water leaving radiance and the corresponding remote sensing reflectance) optical properties of relevance for satellite ocean colour applications. The data were produced through the Coastal Atmosphere & Sea Time Series (CoASTS) and the Bio-Optical mapping of Marine optical Properties (BiOMaP) measurement programs implemented by the Marine Optical Laboratory of the Joint Research Center (JRC) in collaboration with a number of European institutions. Common to both CoASTS and BiOMaP is the standardization of instruments, measurement methods, quality control schemes and processing codes to enforce temporal and spatial consistency to data products. CoASTS measurements comprise 125 field campaigns and 637 stations performed from December 1998 up to March 2016 benefitting of the Acqua Alta Oceanographic Tower (AAOT) in the northern Adriatic Sea to generate time series data at a fixed coastal site. CoASTS data exhibit occurrence of waters with optical properties largely determined by phytoplankton, as well as diverse concentrations of suspended particulate matter (SPM) and of coloured organic matter (CDOM). BiOMaP measurements comprise 36 bio-optical oceanographic campaigns and 1915 stations performed between July 2000 and May 2022 using a variety of oceanographic vessels to produce spatially distributed data across various European Seas. BiOMaP measurement regions include: the Baltic Sea exhibiting waters dominated by a high concentration of CDOM; the Adriatic Sea, Black Sea, North Sea (comprising the English Channel), Ligurian Sea, Iberian Shelf and the Greenland Sea, characterized by a variety of optically complex waters determined by diverse concentrations of CDOM and SPM; the Eastern and Western Mediterranean oligotrophic and mesotrophic Seas.

(a) Station identifier Code Gccssii: G indicates the site or geographic region (V and W for the Acqua Alta Oceanographic Tower (AAOT) in the northern Adriatic Sea, A for Adriatic Sea, B for Baltic Sea, E for Eastern Mediterranean Sea, K for Black Sea, L for Ligurian Sea, N for North Sea, O for Western Mediterranean Sea, I for Iberian Shelf, P for Greenland Sea), while cc indicates the campaign number for the specific region, ss the station number and ii the cast number.