All-weather ultraviolet solar spectra retrieved at a 0.5-Hz sampling rate

A measurement scheme and an algorithm have been developed to retrieve globa l irradiance ultraviolet solar spectra (290-400 nm) at a sampling rate of 0 .5 Hz. The algorithm combines spectral irradiance measurements performed wi th a slow (a few minutes) scanning spectroradiometer (Optronic Model OL752) and a moderate bandwidth multichannel radiometer (Biospherical ground-base d ultraviolet radiometer Model 541.). The filter radiometer instrument allo ws for continuous observations of global UV radiation at five channels (app roximately 10-nm bandwidth), performed simultaneously with spectral measure ments. information about changing cloud conditions during a spectral scan w as retrieved from filter measurements and applied to spectral data, hence e stimated spectra without cloud variations could be constructed. The quality of the estimated spectra depends on data quality from both instruments. Th e method works well in all kinds of weather conditions, as long as the Sun is above the horizon and none of the instruments are hampered by measuremen t errors. (C) 1999 Optical Society of America.