Intercomparison and harmonization of UV Index measurements from multiband filter radiometers

Abstract

[1] Multiband filter radiometers (MBFRs) are extensively used in national measurement networks for UV climate monitoring and for informing the public about potential health risks from excessive solar UV exposure. Results from the first international intercomparison of MBFRs, arranged in Oslo in 2005, are presented. Forty-three radiometers of type GUV, NILU-UV, and UVMFR-7 were assembled, representing monitoring stations on several continents. The first objective was to conduct a blind intercomparison of Global UV Index (UVI) processed by the instrument owners. Eleven independent data sets were compared, eight of which agreed with the reference to within ±5% and ten to within ±10%. The second objective was to provide a harmonized calibration scale for all instruments. When this scale was applied, the UVI agreed to within ±5% (2-sigma) for solar zenith angles (SZAs) up to 90°. The results demonstrate that MBFRs provide accurate UVI measurements for realistic sky conditions and a wide range of SZAs, provided the calibration functions are optimized. The harmonized UVI scale is traceable to the European QASUME reference spectroradiometer.

Long-term comparisons of UV index values derived from a NILU-UV instrument, NWS, and OMI in the New York area

“…In this calibration report as well as the published paper [21] it is stated that the NILU-UV 4115 instrument was harmonized with the campaign UVI reference, with an all-sky median ratio of 1.001 and a 2-sigma standard deviation of the ratio of 0.063 for θ 0 < 80°, where θ 0 is the solar zenith angle. The UVI reference is traceable to the QASUME European reference spectroradiometer.…”

Comparison of ground-based measurements of solar UV radiation at four sites on the Tibetan Plateau

“…A total of 14 NILU-UV instruments participated in an intercomparison campaign (FARIN) in Oslo in 2005 [31]. The cosine responses for all channels were measured for each of the 14 instruments, and very small differences were found between them.…”

Validation of spectral sky radiance derived from all-sky camera images – a case study

“…2) a non-linear regression approach has been applied to obtain all of the spectra in the visible region. This regression method has been applied in various spectral reconstruction applications as described in Johnsen et al (2008), Milton and Rollin (2006) and Dahlback (1996). Non-linear regression is used to determine a relationship between two data sets -namely, the measured spectral radiance from the CCD spectroradiometer and the signal from the three channels of the HSI image.…”

“…Similar spectrometers have been used to measure solar and artificial radiation in Ansko et al (2008); Kouremeti et al (2008); Kreuter and Blumthaler (2009). The system is capable of measuring spectral sky radiance with a spectral resolution of 2 nm between 300 and 800 nm covering the visible part of the spectrum.…”