INTERCOMPARISON OF SPECTRAL-UV-RADIATION MEASUREMENT SYSTEMS

The results of what is to our knowledge the first intercomparison of seven independent spectro-radiometers measuring solar UV irradiances are presented. The intercomparison was carried out in the GSF-Forschungszentrum fur Umwelt und Gesundheit, Neuherberg (near Munich, Germany), on 13 July 1990. The spectroradiometric measurements were supplemented by other meteorological, optical, and chemical measurements at the same time. As this day was cloudless, the data can be compared with the measurements taken by Bener in Switzerland in the 1960's and with the results of radiative transfer models. The measured irradiances at noon differed by factors of up to 100. These large differences demonstrate the great difficulties with this type of measurement. Some instrument systems, however, ranged within tolerances of +/- 10%, thus allowing us to make recommendations for the spectroradiometry of solar UV irradiances.