Ultraviolet climatology over Argentina

Abstract

Satellite-derived climatologies of UV index (UVI) and erythemal daily dose were determined for Argentina at a geographical resolution of 0.5° latitude by 0.5° longitude. Total Ozone Mapping Spectrometer climatology of key input parameters was used to calculate the clear-sky ground-level solar UV irradiance. NASA Surface meteorology and Solar Energy cloud cover data were used to determine the UV attenuation by clouds. Two cases were tested: (1) monthly averages of total cloud cover and (2) monthly averages for three ranges of cloud cover percentage (0-10%, 10-70%, and 70-100%). Case 2, with smaller biases, was selected. Measured erythemal irradiance at seven stations of the Argentine Ultraviolet Monitoring Network was used to validate the satellite-derived climatologies, as well as to estimate aerosol parameters, surface albedo corrections, and UV cloud transmittance for the calculations. Annual average biases of the monthly mean satellite-derived UVI and erythemal daily dose with respect to the ground measurements are mostly within ±10%. The strong longitudinal gradient of UV levels toward the Andes Mountains is emphasized. Very high UVI and erythemal daily dose values are registered in the northwestern tropical high-elevation Andean plateau, with extreme monthly means above 18 and 10 kJ/m 2 respectively, in December-January. Even northern low-elevation regions show averages over 12 and 7 kj/m 2, respectively. On average, clouds attenuate the clear-sky erythemal irradiance by less than 20% for most of the continental region during all months. UV levels are considerably higher than those for equivalent regions in the Northern Hemisphere. Copyright 2006 by the American Geophysical Union.