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 bandwidth multichannel radiometer data was analyzed. The multichannel instrument sampled at both 1 min averages and a high frequency of approximately 0.5 Hz simultaneously with the spectral data. Deviations between multichannel radiometer and spectroradiometer, caused by different angular response (cosine and azimuth), were investigated. Uncertainties due to separate sampling systems and nonideal timing were quantified and removed before data intercomparison. It is shown that high‐frequency multichannel measurements, ideal synchronized to spectral measurements can be used to identify short‐term unexpected errors in spectral measurements down to a level of 5%, limited by the relative angular response error between the instrument during variable cloud conditions.