Variations in the spectral scattering coefficient of marine particles [b p ()] were measured at 241 locations in oceanic (case 1) and coastal (case 2) waters around Europe. The scattering coefficient at 555 nm normalized to the dry mass of particles [b (555)] was, on average, 1.0 and 0.5 m 2 g Ϫ1 in case 1 and case 2 waters, respectively. characterized by a high density that counterbalances the effect of a higher refractive index. In the Baltic Sea, b (555) was similar to values found in other coastal waters despite the fact that particles were dominantly organic, m p which may result from higher absorption relative to scattering. A smaller than expected increase of b p () toward short wavelengths is attributed to significant absorption that increases toward the shorter wavelengths and reduces scattering, whether particles are living, detrital, or mineral. Our analyses suggest that the determination of b may m p be significantly sensitive to the porosity of the filter used to assess the dry mass of particles.Light scattering by suspended particles is generally the first-order determinant of reflectance variability in coastal 1 Corresponding author (marcel@obs-vlfr.fr). AcknowledgmentsThis study was mainly funded by the European Commission (Environment and Climate Program, contract ENV4-CT96-0310), and partially by the European Space Agency and by the U.S. Office of Naval Research Environmental Optics Program (grant N00014-98-1-0003). Ship time was provided by the Reedereigemeinschaft Forschungsschiffahrt and Institut National des Sciences de l'Univers. We thank Louis Prieur, who made possible our participation in the Almofront-2 cruise aboard R.V. L'Atalante. We are grateful to the crews of R.V. Victor Hensen and R.V. Tethys 2, and to Commerc'Air SA staff for their support during field experiments. We also thank G. M. Ferrari, G. Obolensky, N. Hoepffner, F. Lahet, K. Oubelkheir, and E. Roussier for their help during measurements,

A model developed recently by Loisel and Stramski [Appl. Opt. 39, 3001-3011 (2000)] for estimating the spectral absorption a(lambda), scattering b(lambda), and backscattering b(b)(lambda) coefficients in the upper ocean from the irradiance reflectance just beneath the sea surface R(lambda, z = 0(-)) and the diffuse attenuation of downwelling irradiance within the surface layer ?K(d)(lambda)?(1) is compared with measurements. Field data for this comparison were collected in different areas including off-shore and near-shore waters off southern California and around Europe. The a(lambda) and b(b)(lambda) values predicted by the model in the blue-green spectral region show generally good agreement with measurements that covered a broad range of conditions from clear oligotrophic waters to turbid coastal waters affected by river discharge. The agreement is still good if the model estimates of a(lambda) and b(b)(lambda) are based on R(lambda, z = 0(-)) used as the only input to the model available from measurements [as opposed to both R(lambda, z = 0(-)) and ?K(d)(lambda)?(1) being measured]. This particular mode of operation of the model is relevant to ocean-color remote-sensing applications. In contrast to a(lambda) and b(b)(lambda) the comparison between the modeled and the measured b(lambda) shows large discrepancies. These discrepancies are most likely attributable to significant variations in the scattering phase function of suspended particulate matter, which were not included in the development of the model.

Abstract. Coastal Surveillance Through Observation of Ocean Color (COASTℓOOC) oceanographic expeditions were conducted in 1997 and 1998 to examine the relationship between the optical properties of seawater and related biological and chemical properties across the coastal-to-open ocean gradient along the European coasts. A total of 379 stations were visited along the coasts of the Gulf of Lion in the Mediterranean Sea (n = 61), Adriatic Sea (n = 39), Baltic Sea (n = 57), North Sea (n = 99), English Channel (n = 85) and Atlantic Ocean (n = 38). A particular emphasis has been dedicated to the collection of a comprehensive set of apparent (AOPs) and inherent (IOPs) optical properties to support the development of ocean color remote sensing algorithms. The data were collected in situ using traditional ship-based sampling, but also from a helicopter, which is a very efficient means for that type of coastal sampling. The dataset collected during the COASTℓOOC campaigns is still today quite unique in that it is fully consistent in terms of operators, protocols, and instrumentation. This rich and historical dataset is still today frequently requested and used by other researchers. Therefore, we present the result of an effort to compile and standardize a dataset which will facilitate their reuse in future development and evaluation of new bio-optical models adapted for optically-complex waters. The dataset is available at https://doi.org/10.17882/93570 (Massicotte et al., 2023).