Spectral Measurements of Global and Diffuse Solar Ultraviolet‐b Radiant Exposure and Ozone Variations

Since 1985, spectral solar UV‐B radiant exposure has been measured at the High Alpine Research Station Jungfraujoch, Bernese Alps, Switzerland (3576 m). Global (sun and sky) and diffuse (sky) UV‐B radiant exposure on a horizontal plane are measured simultaneously by two identical devices. The detecting system consists of a rotating filter wheel with 8 interference‐filters, centered at every 5 nm between 290 and 325 nm, and a halfbandwidth of ±3 nm. The special advantage of this detector is its waterproofness, allowing operation under all weather conditions. The ratio of the intensities at 305 and 315 nm is being analyzed with regard to ozone variations; for example, the ratio is reduced by a factor of 2 because of an increase in ozone content from 250 to 350 Dobson units. The relation between ozone variations and measured spectral UV‐B intensity is confirmed applying Green's radiation model.