Interannual variations of global UV radiation in Santiago, Chile (33.5°S)

Observations with a four-channel UV radiometer in Santiago, Chile (33.5 degrees S, 70.6 degrees W) from January 1992 to December 1998 are presented. Channels are centered at 305, 320, 340 and 380 nm with a 10 nm bandwidth. Measurements were made at one-minute intervals. Hourly mean values at noon for 305 and 340 nm are presented as well as instantaneous irradiances for 60 degrees of solar zenith angle. Their aperiodic variations on a seasonal scale are discussed with respect to the quasi-biennial oscillation (QBO) and ENSO phenomena. A significant positive trend that must be caused by decreasing total ozone is found in 305 nm irradiance. On a seasonal basis, this negative trend appears strong and significant during winter.