UV radiation in the Alps: the altitude effect

The Alps are one of the regions where the highest UV levels are measured in Europe, which is a consequence of low aerosol levels, high altitude and snow-covered surfaces. Solar UV radiation increases with altitude mainly due to decreasing amounts of air molecules, ozone, aerosols and clouds in the atmosphere. The altitude effect plays a key role in the understanding of the UV radiation field in mountainous terrain. Therefore simultaneous measurements of erythemal UV radiation (broadband) on three different heights were performed in the Swiss Alps during more than four years. Under clear-sky conditions, the altitude effect of daily noon-time yearly mean values of direct, diffuse and global erythemal UV radiation results in 17.4%/1000 m (direct), 8.5%/1000 m (diffuse) and 10.7%/1000 m (global). Seasonal variations of the altitude effect are mainly influenced by changes of solar elevation, albedo values and turbidity levels during the year. In addition, measured altitude effects are shown and compared to calculated altitude effects obtained by application of the MODTRAN radiative transmission model.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.