Comparison of solar UV measurements performed with spectroradiometer and moderate bandwidth multichannel radiometer for different cloud conditions

A method to control spectral global irradiance data using moderate bandwidt h multichannel radiometer data was analyzed. The multichannel instrument sa mpled at both 1 min averages and a high frequency of approximately 0.5 Hz s imultaneously with the spectral data. Deviations between multichannel radio meter and spectroradiometer, caused by different angular response (cosine a nd azimuth), were investigated. Uncertainties due to separate sampling syst ems and nonideal timing were quantified and removed before data intercompar ison. It is shown that high-frequency multichannel measurements, ideal sync hronized to spectral measurements can be used to identify short-term unexpe cted errors in spectral measurements down to a level of 5%, limited by the relative angular response error between the instrument during: variable clo ud conditions.