Working group four of the COST Action 726 "Long term changes and climatology of UV radiation over Europe" is responsible for the Quality control of erythemally weighted solar irradiance radiometers. One major task of this activity was the organisation of a characterisation and calibration campaign of reference radiometers in use in regional and national UV networks in Europe. The campaign was organised at the PMOD/WRC from 28 July to 23 August 2006; it is located in the Swiss Alps at 1610 m a.s.l. A total of 36 radiometers from 16 countries participated at the campaign, including one radiometer from the Central UV Calibration Facility, NOAA, U.S.A.
The radiometer types represented at the campaign were 9 Yankee UVB-1, 5 Kipp & Zonen, 2 Scintec, 11 analog and 8 digital Solar light V. 501, 1 Eldonet and 1 SRMS (modified Solarlight V501). A second spectroradiometer from the Medical University of Innsbruck, Austria participated as well to provide redundant global spectral solar UV irradiance measurements; this spectroradiometer agreed with the QASUME spectroradiometer to within ±2% over the two week measurement campaign. The atmospheric conditions during the campaign varied between fully overcast to clear skies and allowed a reliable calibration for the majority of instruments.
A novel calibration methodology using the spectral as well as the angular response functions measured in the laboratory provided remarkable agreement with the reference spectroradiometer, with expanded uncertainties (k=2) of 7% for the most stable instruments. The measurements of the broadband radiometers were analysed both with the PMOD/WRC provided calibration as well as the prior calibration from the home institutes. The relative differences between the measurements using the prior calibration and the reference spectroradiometer varied between excellent agreement to differences larger than 50% for specific instruments.
Gröbner, J., Hülsen, G., Vuilleumier, L., Blumthaler, M., Vilaplana, J.M., Walker, D. and Gil, J.E., 2007. Report of the PMOD/WRC-COST Calibration and Intercomparison of Erythemal radiometers. ftp. pmodwrc. ch/pub/publications/PMOD_COST726_BBreport. pdf.
Categories: Photonics & Optoelectronics