Aspects of quality assurance in monitoring solar UV irradiance

More quality assurance activities are needed to minimize uncertainties and improve equivalence of the UV radiation data obtained at different sites worldwide in order to monitor trends and to determine changes due to the depletion of the stratospheric ozone layer. Aspects of traceability based on a calibration chain from a cryogenic radiometer to the spectroradiometers within a UV monitoring network, as well as equivalence and conformity based on intercomparisons of standard lamps and instruments, are discussed. Some recent developments to be used for quality assurance/control in UV monitoring networks are presented, covering portable monitor radiators, monitor systems containing photodiodes and/or LEDs as well as the calibration transfer from the horizontal to the vertical optical axis.