Comparison of ultraviolet spectroradiometers in Antarctica

[1] Solar ultraviolet irradiance has been monitored in Antarctica for almost two decades by a network of spectroradiometers established by the National Science Foundation. Data have been used for investigating increases in ultraviolet radiation in response to ozone depletion, validation of satellite observations, and the establishment of ultraviolet radiation climatologies and trends. To assess the quality of data collected, measurements of the monitoring spectroradiometer installed at Arrival Heights (78°S, 167°E) were compared with an independently calibrated, state-of-the art instrument, which was installed next to the monitoring system for a three-month campaign. Measurements of the two instruments differed by 5–7% on average. The discrepancy is quantitatively explained by the different irradiance scales used by the two systems, a bias in determining the reference plane of fore-optics, drifts of calibration standards, some temperature-dependence in the transmission of the entrance optics, and nonlinearity of one of the systems. The wavelength accuracy of data from both instruments was also tested with two commonly used correlation methods. Wavelength shifts determined with the two methods agreed to within 0.003–0.006 nm. Results of the campaign suggest that data collected by the monitoring instrument are of adequate quality for submission to the Network for the Detection of Atmospheric Composition Change.