Effects of meteorology and tropospheric aerosols on UV-B radiation: a 4-year study

Broadband Ultraviolet-B (UV-B, 280-315 nm) and total (300-3000 nm) radiation measurements and calculations have been carried out in Cordoba City, Argentina (31degrees 24'S, 64degrees11' W, 470 m above sea level) between November 1998 and December 2002. UV-B measurements were carried out with a YES UVB-1 radiometer while calculations were performed using the tropospheric ultraviolet visible model (TUV 4.1). Total measurements were taken using a YES TSP-700 pyranometer and the calculations using a parameterization. The site selected for the measurements represents semi-urban conditions and is along the most frequent wind direction (NE-SW) with respect to the city center. For clear sky days, calculations showed a good agreement with measurements. However, this study showed a substantial reduction (up to 50%) in the UV-B radiation on days with high levels of aerosols. The default aerosol properties included in the model did not account for the observed reductions. A four-day-aerosol-loading episode was analyzed. Relationships between measurements and calculations were used to derive specific information about the aerosols present on those days. In this work we analyzed the hourly, seasonal, and interannual variations of the measured UV-B solar noon values in order to assess the aerosol influence on each of them. Both UV-B and total irradiance showed a systematic reduction every winter-spring period. The origin of the aerosols and the causes for this behavior are also discussed. (C) 2004 Elsevier Ltd. All rights reserved.