The Atacama Surface Solar Maximum

S urface solar radiation is a major component of the surface heat budget. Diurnally and seasonally averaged over the entire Earth, 188 ± 7 W m–2 reach the surface to be either absorbed (~165 ± 6 W m–2) or reflected back to the atmosphere (Trenberth et al. 2009; Stephens et al. 2012). Changes in the amount of solar radiation received at the surface are intrinsically tied to the total amount of precipitation through the surface heat balance (e.g., O’Gorman and Schneider 2008). Surface solar radiation is also a critical flux in the heat balance of both oceans and ice sheets (Reed 1977). Photosynthetic life forms owe their existence to the solar radiation in the visible part of the spectrum reaching the surface of the planet. On the other hand, the existence of bacterial life, for instance, can be limited by an excess of radiation in the ultraviolet (UV) part of the spectrum (Cockell et al. 2008). Moreover, exploiting surface solar radiation for energy production has become a major societal goal as the accessible fraction of the solar energy reaching Earth’s surface is potentially several times the energy required for sustaining civilization. For a given point at the surface of the planet, the amount of global or total horizontal solar radiation that can be measured by a broadband pyranometer [i.e., an instrument that measures the global solar irradiance, or the sum of direct plus diffuse radiation, typically over wavelengths between 0.2 and 3 mm (e.g., Iqbal 1983)] is dependent on 