## 3 Results
### Comparison of Atmospheric Parameters  
To assess the optical characteristics of dust aerosol for the period from 27 September to 30 September 2020, the measurement data obtained using the SPM photometer were analyzed. According to the in situ data obtained from the R/V \"[PERSON]\" in the Kerch Strait region, the average daily value of the aerosol optical thickness 27 September was 0.3 and = 0.16 for AOT (500) and AOT (872), respectively; for September 29, AOT (500) = 0.27 and AOT (872) = 0.18 and for 30 September, AOT (500) = 0.26 and AOT (872) = 0.15, which is more than 1.5 times the monthly average value of AOT (500) (0.156) and AOT (872) (0.09). Analysis of the fine- and coarse-mode aerosol fraction's contribution to the total value of AOT for the days under study revealed that on more than 70% of the days, the atmospheric aerosol consisted of particles from the fine-mode fraction. The average daily water vapor content for the period from September 27 to September 30 exceeded the monthly average values by more than 1.5 times, confirming that these particles contained condensed water vapor. The aerosol optical thickness at a wavelength of 500 nm was obtained from measurements of the attenuation of direct solar radiation by the SPM photometer on 10.09.2020. AOT (500) was 0.12, which is less than the monthly average value of AOT (500) of 0.16. On 10.09.2020, analysis of the coarse-dispersed suspension's contribution to the total distribution of the aerosol optical thickness showed the presence of both large (>1 \(\upmu\)m) particles (30%) and the fine fraction (70%). Measurement data from the Atmas dust analyzer also showed low concentrations of both large particles (PM10 = 0.016) and smaller particles (PM2.5 = 0.01) on this day. The monthly averages  
Figure 5: Satellite image (VIIRS) of dust transport over the Black Sea on 27.09.2020 (**a**) and the 7-day back trajectories of airmass transport at Sevastopol station (central part of the Black Sea) (**b**). for September were 0.017 and 0.01 for PM10 and PM2.5, respectively. Unfortunately, no Atmas data for 27 September 2020 were available; however, on the eve of 26 September 2020, the concentration of PM10 particles reached 0.03, which indicated the presence of coarse particles in the atmosphere. As the clouds developed and moved, they precipitated onto the underlying surface of the study region. By analogy with the case of 12.09.2017, we considered the Ocean Color L2 data for the selected date from the VIIRS and MODIS (Aqua) satellites. From 27 September 2020-29 September 2020, AOT over the Mediterranean and Black Seas reached the limit values, namely > 0.4. In the Black Sea, according to the MODIS data, an area of 166,855 pixels was identified. For a comparative analysis of the day on which dust transport occurred and the day on which the atmosphere was clean, the nearest possible date was 10.09.2020. This time interval is caused by a number of factors, including extensive cloudiness, dust transport with clouds, and strong Sun glint (Figure 6). The fundamental difference from the previous date of this case is the lower percentage of Sun glint, specifically 20% of the total number of valid pixels from the L2 data (on 12.09.2017, MODGLINT was present in 59% of the pixels) (Figure 7). Figure 6: Spatial distribution of MODIS AOT values from a clean atmosphere over the Black Sea on 10.09.2020 (**a**) and dust transfer on 27.09.2020 (MODIS) (central part of the Black Sea) (**b**), 29.09.2020 (**c**) (MODIS) and VIIRS (**d**) (source: SeaDas). Thus, we selected a site in the central-eastern region of the Black Sea for which a comparative analysis of the L2 and L3 data was carried out. In a similar way, on 29 September 2020, an analysis of the hydro-optical characteristics of the eastern part of the Black Sea during dust transport from the Sahara was carried out. It was also confirmed by back trajectories and measurements using a portable spectrophotometer, SPM. According to the VIIRS and MODIS data, the following values were obtained (Table 3).