The Hyperspectral Bio-Optical Observations Sailing on Tara (HyperBOOST) dataset

Abstract. During the Tara Europa Expedition, the HyperBOOST (Hyperspectral Bio-Optical Observations Sailing on Tara) team, part of the larger research program TREC (TRaversing European Coastlines), carried out the collection of discrete and continuous measurements to explore the bio-optical properties of water at the land-sea interface. During the 409 days of the expedition between April 2023 and August 2024, 202 HyperBOOST stations were sampled along the European coastlines, including the Baltic Sea, the North Sea and the Mediterranean Sea. Discrete biogeochemical samples were collected in triplicate at all stations using Niskin bottles, including dissolved and particulate organic carbon, suspended particulate matter, chlorophyll a and other biologically relevant pigments, as well as samples for dissolved and particulate absorption. Along-track continuous AOP measurements were carried out using a So-Rad (solar tracking radiometry platform), while IOPs were collected and processed through the automated In-line system/software. After binning and quality control, 236,567 one-minute binned particulate absorption and attenuation spectra, 26,589 five-minute binned back-scattering spectra, and 7001 five-minute binned So-Rad reflectance spectra were available for further analyses and colocation with the station data. Overall, the Tara Europa expedition allowed to systematically sample European coastal waters at unprecedented temporal and spatial coverage, crossing regions characterized by a wide range of optical and biogeochemical conditions. The combined use of different instruments or measurements approaches also provided the opportunity to assess the internal consistency of the dataset by performing several optical closure assessments. The HyperBOOST dataset provides a valuable resource for advancing and evaluating existing and devising novel bio-optical models in optically diverse waters, enhancing satellite ocean-colour applications and product validation.