Calibration and uncertainty estimation of erythemal radiometers in the argentine ultraviolet monitoring network.

The erythemal radiometers of the Ultraviolet Monitoring Network of the Argentine Servicio Meteorológico Nacional were calibrated in an extensive in situ campaign from October 1998 to April 1999 with Austrian reference instruments. Methods to correct the influence of the location's horizon and long-term detector changes are applied. The different terms that contribute to the measurement uncertainty are analyzed. The expanded uncertainty is estimated to be +/- 10% at 70 degrees solar zenith angle (SZA) and +/-6% for a SZA of <50 degrees. We observed significant changes for some detectors over hours and days, reaching a maximum diurnal drift of +/-5% at a SZA of 70 degrees and a maximum weekly variation of +/-4%.