Our work’s primary goal is to reveal the problematic issues related to estimates of the colored organic matter absorption coefficient in the northern seas from data of the Ocean and Land Color Instrument (OLCI) installed on the Sentinel-3 satellites, e.g., a comparison of the OLCI standard error assessment ADG443_NN_err relating to the measurement and the retrieval of the geophysical products and the uncertainties in the northern seas’ real situation. The natural conditions are incredibly unfavorable there, mainly due to frequent cloudiness and low sun heights. We conducted a comprehensive multi-sensor study of the uncertainties using various approaches. We directly compared the data from satellites (OLCI Sentinel-3 and four other ocean color sensors) and field measurements in five sea expeditions (2016–2019) using the different processing algorithms. Our analysis has shown that the final product’s real uncertainties are significantly (≥100%) higher than the calculated errors of the ADG443_NN_err (~10%). The main reason is the unsatisfactory atmospheric correction. We present the analysis of the various influential factors (satellite sensors, processing algorithms, and other parameters) and formulate future work goals.

Data on the light absorption by seawater and its components are needed in many theoretical and practical aspects of marine science and engineering. However, up to now, there is a lack of such data for the northeastern part of the Black Sea. This article presents the data on light absorption measured by a portable integrated cavity absorption meter (ICAM) spectrophotometer in the Gelendzhik region of the Black Sea during field studies in June 2017 and 2018, together with other bio-optical and oceanographic data from in situ measurements and satellite observations. In 2018, the elevated values of the colored dissolved organic matter (CDOM) absorption in the surface layer were observed concurrently with high values of salinity, contradicting the idea of river runoff being the main CDOM source. The vertical profiles of salinity differed in 2017 and 2018, especially in shallow waters; in the upper layer, the salinity increased from 17.1 psu in 2017 to 17.8 psu in 2018, while the values of CDOM absorption increased from 0.10 to 0.16 m−1. The analysis of available hydrometeorological data pointed to intensive vertical mixing due to the strong wind forcing as a main factor in increasing values of both salinity and the CDOM absorption in the surface layer in 2018.

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Цель выполненных исследований -получение для северо-восточной части Черного моря комплекса данных оптических и сопутствующих измерений в сочетании с данными спутниковых наблюдений для усовершенствования спутниковых методов оценки биооптических характеристик вод поверхностного слоя.Были поставлены следующие основные задачи: -натурные измерения комплекса оптических характеристик: спектральных коэффициентов яркости водной толщи; спектральной облученности поверхности моря и на разных горизонтах в водной толще, создаваемой нисходящим и восходящим потоками солнечного излучения; вертикальных профилей показателя ослабления света; спектральных показателей поглощения света морской водой; спектров флуоресценции растворенного органического вещества (РОВ) и Chl-a, возбуждаемой лазерным излучением разных спектральных диапазонов; глубины видимости белого диска (относительной прозрачности морской воды); -одновременные измерения гидрологической структуры вод и вертикального распределения флуоресценции Chl-a посредством CTD-зонда;

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