From the UV database prepared by ARMINES (Prof. L Wald), an atlas of UV irradiation has been developed by averaging daily UVA and UVB irradiations per month and for four 5-year periods (1988-1992; 1993-1997; 1998-2002; 2003-2007) for Europe as a whole and for individual countries in the region, for UVA, UVB and total UV irradiations, at both absolute and relative levels.
UV irradiation levels were initially extracted from surface solar irradiance derived from the Meteosat satellite’s images. From these irradiation levels, the UV component is computed by a model which exploits the algorithm set up by the Royal Institute of Meteorology, Belgium, published in the European Solar Radiation Atlas (spectral model of Joukoff ESRA). The algorithm converts the total irradiance (E) into its spectral distribution E(λ), every 10nm, starting at 310nm. The clearness index KT is: KT = E/E0, where E0 is the irradiance at the top-of-atmosphere.
Data were made available on the SoDa website ( solar radiation data) with web-based tools to extract data from 1985 for UVA and UVB irradiance for every geographical area in Europe (grid cell of 5km). Due to the orbit of the Meteosat satellite, data from the far north of Europe was not available. This however has a minor impact in respect to the population size and density in this area.
UV bandwith were defined according to WMO standard (WMO no8, guide to meteorological instruments and methods of observation), with UVA defined from 315 nm to 400 nm; and UVB from 280 nm to 315 nm.
The value of UVB should not be confused with erythemal UV or CIE Standard Erythema Dose.