Spectral ultraviolet measurements by a multichannel monitor and a brewer spectroradiometer: a field study.

Two different instruments for measuring the spectral UV irradiance were used in a field comparison study in July 2000 in Rome, Italy: a Brewer spectrophotometer and a moderate-bandwidth filter radiometer (GUV-511C). The Brewer is designed to measure the solar spectral irradiances in the region from 290 nm to 325 nm with a spectral resolution of 0.5 nm. The GUV-511C measures hand-averaged spectral irradiance at four wavelengths: 305, 320, 340 and 380 nm with a bandwidth depending on the filter type for each channel (about 10 nm full width half maximum, FWHM). Comparisons between the two instruments were made for 5 days for the two wavelengths 305 and 320 nm under different meteorological conditions with the Brewer taken as the reference.