As a consequence of stratospheric ozone depletion and due to the current uncertainties in the Earth's climate, ultraviolet radiation observations are becoming increasingly important and nowadays form a part of many radiation monitoring networks. UV irradiance is commonly measured either with spectrophotometers or with filter instruments. While the most accurate UV radiation measurements are obtained from high-resolution UV spectrophotometers, routine observations for public health assessment and long-term measurements are performed with wide-band UV filter radiometers (UV-B or Erythemal weighting) as they are simple to maintain.

Due to the physical limitations of filter materials and detectors, the spectral response functions of wide-band UV radiometers are not identical to theoretical spectral sensitivities. Such a spectral mismatch introduces discrepancies between measured and real UV radiative quantities. If the spectral mismatch of the radiometers and the calibration measurement conditions are accounted for in the calibration procedure the measurement accuracy is considerably increased. By using modelled UV spectra the improved measurement accuracy can be expanded to other measurement conditions that were not encountered during calibration, including variations in ozone column density and optical depth.

The paper gives a summary of the new calibration procedure and describes the best estimate of the calibration uncertainty obtained from the uncorrected and the corrected calibration method. The results obtained from the described UV calibration method are compared to those published in related documents.