The west coast of southern Africa (WCSA) is a key region of the Earth’s system. It is characterized by a semi-permanent and extensive stratocumulus (Sc) cloud deck (Figure 1) formed under a strong subsidence inversion of the anticyclonic circulation above the cool waters of the oceanic upwelling zone (Tyson and Preston-Whyte, 2000). Low-level Sc clouds increase the net amount of outgoing radiation at the top of the atmosphere (TOA), inducing the most negative radiative effect of any cloud regime (Boucher et al., 2013). The properties of the South Atlantic Sc strongly affect the temperature gradients of the Atlantic Ocean’s surface waters and large-scale energy balance, which could influence the position of the ITCZ, large scale atmospheric features such as the West African and Asian monsoons, and precipitations as far as in the Amazonian region of Brazil (Jones et al., 2009; Jones and Haywood, 2012; Roehrig et al., 2013). The WCSA is also know for the northern Benguela upwelling system (nBUS), located off the west-coast of Namibia, south of the Angola-Benguela front (~17°S) and north of the strong upwelling cell at Lüderitz (26°S). This gives rise to a complex and highly variable ecosystem (Shannon and Nelson, 1996), characterized by perennial coastal and open-ocean upwelling, mostly wind-driven but modulated by several atmospheric and oceanographic processes (Wasmund et al., 2016).
As a consequence, the nBUS is one of the most productive marine ecosystems in the world, promoting high primary plankton production and fish populations (Jarre et al., 2015; Louw et al., 2016). Future climate projections point to Southern Africa as a region where severe warming will occur (IPCC, 2013). Under the pessimistic RCP 8.5 emission scenario, the south-western regions (parts of South Africa, Namibia and Botswana) are projected to experience future increase in temperature up to 1.5 °C–2.5 °C, particularly during the September–October–November season (Maure et al., 2018). A larger fraction of land is projected to face robust decreases in precipitation between 0.2 and 0.4 mm day−1 (around 10%–20% of the climatological values). These are expected to be accompanied by increases in the number of consecutive dry days and decreases in consecutive wet days over the region. These projected changes imply significant potential risks to agricultural and economic productivity, human and ecological systems, health and water resources (Lennard et al., 2018; Maure et al., 2018). For instance, they could affect the development of coastal fog, the major source of water for the endemic flora and fauna, and human settlements in the arid Namibian ecosystem (Seely, 1979; 1998; Olivier, 1995). The projected regional climate change would affect the strength and the dynamics of the nBUS (Bakun et al., 2010), thereby the oceanic primary production and availability of livestock in the area, affecting fishery, a major resource for the local economies (Jarre et al., 2015). Such changes also could lead to the insurgence of hypoxic conditions and phytoplankton breakdown affecting the emissions of toxic hydrogen sulfide and greenhouse gases (Carr, 2002), and ultimately the sequestration of carbon dioxide (Keeling et al., 2010).