Monitoring of Solar Irradiance in the High Andes.

Solar radiation has been measured in the high Andes near Laguna Lejia (latitude 23° 26' 23.30" S, longitude 67° 38' 14.29" W) at an elevation of 4715 m between December 2016 and December 2017. Irradiances were monitored in four wavelength channels: PAR (400-700 nm), UV-A (315-400 nm), UV-B (295-315 nm) and short-wavelength UV-B (295-310 nm) with a new radiometer. In addition, ambient temperatures were recorded. Record values have been found for PAR (exceeding 600 W m-2 ), UV-A (close to 95 W m-2 ), UV-B (3.13 W m-2 ) and short-wavelength UV-B (0.144 W m-2 ) during Austral spring. The winter irradiance values slightly exceeded 50% of these values. Maximal cloud effects due to multiple reflections were 45, 38, 32 and 35% higher than values under cloudless skies for PAR, UV-A, UV-B and short-wavelength UV-B, respectively. Record irradiance for this site shows a UV index reaching and exceeding 20, which is due to low solar zenith angles, the altitude, low water vapor and aerosol concentrations in the atmosphere as well as low total column ozone concentrations.