## 1 Introduction
Aerosol optical thickness (AOT sometimes appear as AOD) is an indicator of the variability of the optical properties of the atmosphere due to the correlation between the concentrations of aerosol particles and light attenuation coefficients, the data for which are obtained through the widespread use of satellite remote sensing methods [8; 9; 10]. One of the informative hydro-optical characteristics of seawater is the reflectance coefficient or remote-sensed reflectance (Rrs). It is almost entirely determined by substances that are suspended and dissolved in seawater. This characteristic is important for understanding the biogeochemical processes that occur in the surface layer, such as primary production, the response of the marine ecosystem to climatic changes, etc. [11; 12]. Calculations of Rrs at sea level from Rrs at the top of the atmosphere require atmospheric correction. Therefore, Rrs at sea level directly depends on the contribution of the aerosol component in atmospheric radiance since aerosols are highly variable and can significantly distort the results of atmospheric correction. Atmospheric correction, including the estimation of aerosols' contribution, is performed according to the methodology proposed by [PERSON] and [PERSON] [13], with updated aerosol models and approaches to the selection of these models [14]. This algorithm is based on the measurements of 2 sensors in the near infrared (e.g., 748 and 869 nm for MODIS), where the contribution of upwelling sea radiance is usually small and can be accurately estimated using the iterative approach to bio-optical modeling [15]. The purpose of this study was to research the effect of dust aerosol on error in the restoration of the spectral reflectivity of seawater and the aerosol optical thickness (AOT) using remote sensing methods (namely, atmospheric correction algorithms based on MODIS satellite data) and ground measurements based on AERONET network measurements. To achieve this goal, a comparative analysis of the optical characteristics of a day (1) on which dust aerosol was present in the atmosphere and (2) a day on which the atmosphere was clean was performed. The main object of research was the Black Sea, which has been studied for many decades by researchers and scientists from the Marine Hydrophysical Institute of the Russian Academy of Sciences (Sevastopol) [16]. Studies investigating the influence of absorbing aerosols on the optical characteristics of the atmosphere and surface layer of the Black Sea were initiated in the early 2000s [17; 18] and have been urgent until now. With the advent of new instruments and higher-resolution satellite information, events and phenomena occurring in the atmosphere over the study area can now be described more accurately. Further comparison of the values of Rrs(\(\lambda\)), obtained by remote sensing, with their typical values based on decades of statistics and observation values serves as a criterion of reliability algorithms for atmospheric correction [19; 20; 21]. The relevance of this work is that incorrect consideration of the atmospheric component (presence of dust, biomass combustion products, industrial emissions, etc.) can distort the values of the restored Rrs(\(\lambda\)) values for the Black Sea and subsequently lead to large errors in the calculation of chlorophyll concentrations [19]. Every year, from March to October, many occurrences of dust transfers are recorded over the Sevastopol and Black Sea region, mainly from the southwest direction (Saharanan dust) [21; 22; 23]. It is known that dust aerosol particles in the atmosphere have a significant impact on climate change, air quality, and the state of the ecosystem as a whole. Measurement of the optical and microphysical characteristics of dust aerosols using remote sensing methods is associated with several difficulties as dust particles show significant variability regarding their size, shape, and chemical composition, depending on the origin (region) and meteorological conditions.