Erythemal ultraviolet irradiance in Córdoba, Argentina

Biologically active solar Ultraviolet-B radiation (UVery, 280–315 nm) is monitored in Córdoba, Argentina (31°24′S, 64°11′W, 400 m a.s.l) using the Yankee Environmental Systems (YES) pyranometer, model UVB-1. Measurements of the solar broadband UV-B irradiances are presented for the period of November 1998–December 1999. The site selected for the measurements represents semi-urban conditions and is along the most frequent wind direction (NE–SW) with reference to downtown, following the direction of prevailing winds. For clear sky days, the measurements are in good agreement with results of a radiative transfer model. However, examination of the record of solar ultraviolet measurements showed substantial reduction of the UV-B radiation on days with high levels of air pollution, which are associated with high concentration of particulate matter. Particulate matter is the only pollutant that surpasses the air quality standard several times during the year in Córdoba City. In this work, we investigate the daily variation of the UV-B radiation to assess its response to air pollution, physical variables, and meteorological factors. The main findings are that tropospheric aerosol is the most important UV-B attenuating factor (up to 40%), whereas tropospheric ozone and other UV absorber air pollutants like SO2 are not important. The results are consistent with the fact that pollution in Córdoba has mostly primary character with CO, NOx, and PM10 being the most important air pollutants. The UV-B radiation correlates well with simultaneous records of total radiation, but the reduction factors reflect stronger effects on the UV radiation than on total radiation.