## 5 Conclusions  
A comparative analysis of the spectral brightness coefficient values obtained from the results of satellite measurements on days on which dust transport occurred in the atmosphere (12.09.2017, 27.09.2020, and 29.09.2020) and days on which the atmosphere was clean (08.09.2017 and 10.09.2020) showed that in the presence of dust aerosol, even with the maximum pixel quality (L3), the spectral luminance factor in the shortwave region had negative values. Moreover, the spectral brightness coefficients obtained on a day on which the atmosphere was clean were 20% higher than on a day on which dust transfer occurred. Thus, the correlation of the Rrs(\(\lambda\)) values for the L2 data was 83% and for L3, it was 84%.  
For intense dust transport with a clear predominance of the coarse fraction on 27 September 2020, and the next day, on which the atmosphere was clean (10 September 2020), the correlation was 28% for L3 and 27% for L2, which is a low indicator of the atmospheric correction quality of the results for this period of intense dust transfers. For all dates except 12 September 2017, a sharp increase (by a factor of 2) in the chlorophyll-a concentration between the 2 dates was obtained, which is not typical for the Black Sea region.  
Comparative analysis of the satellite and in situ data results revealed that even with identical or close AOT and Angstrom parameter values, the correlation of the in situ and satellite spectral brightness coefficients was 79%, with a clear tendency to underestimate the actual values. For the day on which the atmosphere was clean, 08.09.2017, despite the presence of turbidity according to the MODIS data, the correspondence of the values was 88%.  
The Rrs(\(\lambda\)) values for L2 and L3 levels on a day on which the atmosphere was clean during winter (10 February 2021 and on 27 February 2021), the correlation was 99%. However, considering the dust transport effect on the restoration of the sea brightness coefficients (correlation between a day on which the atmosphere was clean and a day on which the atmosphere was dusty), the coefficient decreased to 53% for L3.  
It is also worth noting that this study showed that a specific set of error flags can also serve as an indicator of dust, and specifically, in almost all cases, the combination included STRAYLIGHT, ATMWARM, TURBIDW, LOWLW, and MODGLINT.  
The results obtained confirmed that the error in the values of the atmospheric correction of 16-17% was caused by dust aerosol. This fact also confirms that on days on which dust transfer occurs, it is necessary to carry out an additional atmospheric correction, and in situ measurements are also required in the studied region, as two points (AERONET stations) on the coast of the western part of the Black Sea cannot enable correct validation of satellite and field data.  
Conceptualization, D.V.K. and A.S.P.; methodology D.V.K. and A.S.P.; formal analysis, A.S.P. and D.V.K.; investigation, A.S.P. and D.V.K.; data curation, A.S.P. and D.V.K.; writing--original draft preparation, D.V.K.; writing--review and editing, D.V.K. and A.S.P.; visualization, D.V.K. and A.S.P. All authors have read and agreed to the published version of the manuscript.  
This research was carried out in the framework of Russian Federation state task#0555-2021-0003 \"Operational oceanology\", and RFBR grant 19-05-50023 and 19-35-90066.  
The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** The authors thank [PERSON], [PERSON], [PERSON] and [PERSON]'s group from NASA for the pre-delivery of AOT data, calculations of BTA data, processing of measurements obtained at the Sevastopol AERONET station, and for the possibility of using high-quality photometric measurement data. The authors also express their gratitude to [PERSON] and [PERSON] for providing the SPM photometer and its software.  
**Conflicts of Interest:** The authors declare no conflict of interest.