## 3 Results and Discussion
### Aerosols, Clouds, and Solar Fluxes during the Evolution of DAEC
Even higher SSA values (larger than 0.98, deep red colors) exist over the Atlantic Ocean, where dust and other continental aerosols are absent, in contrast to the closed Mediterranean Sea surrounded by European and African land areas. Regarding the geographical distribution of MERRA-2 AP, it varies between 0.74 and 0.76 over both N. Africa and dust export regions (Figure S9), indicating the dominance of DA [74]. In general, larger AP values occur over areas with coarse maritime and dust aerosol loadings. Figure 2: Geographical distribution of MERRA-2 DOD (left column, (i)) and ISCCP-H cloud amount (right column, (ii)) during the day before (first row, (a)), the first (second row, (b)), second (third row, (c)), third (fourth row, (d)), and the day after (fifth row, (e)) the DAEC that took place during 16-18 June 2016 over the Mediterranean Basin. Results are given at 12:00 UTC of each day. Apart from the aerosol optical properties, the DDREs are strongly dependent on the available solar radiation fluxes [55]. These fields, namely the absorbed solar radiation at the TOA, in the atmosphere, and at the surface of the broader MB, including the African dust export areas, are given in Figure 3. The solar radiation fluxes are computed for all-sky conditions, i.e., including the presence of clouds, during the three days of the DAEC and are given at 12:00 UTC of each day. At the TOA, the absorbed solar radiation fluxes (Figure 3, first column) are strongly influenced by clouds (Figure 2, second column) and secondarily by other parameters such as aerosols and surface albedo. On the first DAEC day, the absorbed solar fluxes at the TOA vary from 450 to 1150 W/m\({}^{2}\), with lower values over areas covered by clouds, such as the northwestern Algerian coasts, and over the areas along the axis extending northeasterly, passing over the Balearic Sea and reaching up southeastern France and the Alps, as well as the areas along a second axis of cloud-covered areas extending northeasterly from the Tunisian coasts over the Tyrrhenian Sea, central Italy, and up to the northern Adriatic Sea (see Figure 2). Nevertheless, not all similarly cloud-covered areas absorb the same solar radiation. For example, clouds along the second axis, in the central MB, absorb significantly less SW radiation than clouds along the first axis, in the western MB, by as much as 100-200 W/m\({}^{2}\), though having similar cloud fractions (larger than 0.8-0.9, Figure 2 ii-a). These differences are attributed to the different cloud optical thickness (COT) of these two cloudy areas, being about 6 to 24 in the western and less than 5 in the central MB (Figure S8), highlighting the primary role of COT in the perturbation of solar radiation [65; 75]. In contrast, the highest absorbed solar fluxes at the TOA (larger than 1000 W/m\({}^{2}\)) are observed over the cloud-free Mediterranean Sea areas, which also have low surface albedo. The role of surface albedo is evidenced by the significant differences (of about 200 W/m\({}^{2}\)) between the TOA-absorbed SW values over the low-surface-albedo central and eastern Mediterranean Sea (deep reddish colors) and the more reflective adjacent continental coastal areas of North Africa (Libya and Egypt, greenish and yellowish areas). Similar findings, underlying the primary role of clouds and surface albedo for the absorbed solar flux at the TOA, are found for the second and third days of the DAEC (Figure 3i-b and Figure 3i-c, respectively). The geographical patterns of the atmospheric absorbed solar radiation (second column in Figure 3) are governed by clouds and aerosols as well as the available solar radiation. Most aerosols, except for strongly scattering ones such as sulfate and sea-salt, increase the SW atmospheric absorption. On the other hand, clouds strongly scatter the SW radiation, while modifying (increasing or decreasing) the absorbed solar radiation in the atmosphere through different mechanisms.