Comparison of two methods for cloud flagging of spectral UV measurements

This paper compares two methods of cloud flagging that were developed at th e Deutscher Wetterdients (DWD) and at the Laboratory of Atmospheric Physics , University of Thessaloniki (LAP). The two methods are applied to the same data set to uncover their similarities and differences. The LAP method aim ed at flagging the quality of global UV irradiance spectral measurements wi th respect to the purity of their spectral characteristics. while the DWD f lags describe the sky conditions and their effects on the radiation field i n an absolute sense as well as their short-time variability. In this respec t, the two methods appear to have distinct differences, and also similariti es, in describing when the sun's disk is occluded or not. (C) 2001 Elsevier Science B.V. All rights reserved.