*3.3. Spatial Distribution of MERRA-2 SAOD and AAOD*

Scattering aerosol optical depth (SAOD) could be obtained by subtracting absorption aerosol optical depth (AAOD) from the total aerosol optical depth (TAOD) [50]. Mean values of MERRA-2 SAOD and AAOD between 1980 and 2020 over the SCS were shown in Figure 5. In Figure 5a, the spatial distribution of SAOD was similar to AOD distribution in Figure 2. SAOD was high in the north and low in the south, and gradually decreased from the north to south over the SCS. On the whole, SAOD was a little lower than AOD over the SCS. The north of the SCS showed more obvious SAOD variation. The highest SAOD between 0.325 and 0.375 occurred in the offshore area of China, while the lowest SAOD between 0.125 and 0.15 could be observed in the south of the SCS. In the middle of the SCS, SAOD was between 0.15 and 0.175. As shown in Figure 5b, high AAOD (0.015–0.0175) appeared in the north and low AAOD (0.0025–0.005) was in the south of the SCS. AAOD gradually decreased from the north to the south. More obvious AAOD variation could be observed in the north of the SCS. In the middle of the SCS, AAOD was between 0.005 and 0.0075. Over the entire SCS, AAOD was much lower than SAOD, indicating scattering extinction played a major role in this area.

**Figure 5.** Spatial distribution of mean values of (**a**) scattering aerosol optical depth (SAOD) and (**b**) absorption aerosol optical depth (AAOD) over the SCS in the period of 1980–2020.
