Atmos. Chem. Phys. Discuss., 8, 1415-1455, 2008
www.atmos-chem-phys-discuss.net/8/1415/2008/
doi:10.5194/acpd-8-1415-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Quality assurance of the Brewer UV measurements in Finland
K. Lakkala1, A. Arola2, A. Heikkilä2, J. Kaurola2, T. Koskela2, E. Kyrö1, A. Lindfors2, O. Meinander2, A. Tanskanen2, J. Gröbner3, and G. Hülsen3
1Finnish Meteorological Institute, Arctic Research Centre, Sodanlylä, Finland
2Finnish Meteorological Institute, Helsinki, Finland
3Physikalisches Meteorologisches Observatorium Davos, World Radiation Center, Davos Dorf, Switzerland

Abstract. The quality assurance of the two Brewer spectrophotometers of the Finnish Meteorological Institute is discussed in this paper. The complete data processing chain from raw signal to high quality spectra is presented. The quality assurance includes daily maintenance, laboratory characterizations, calculation of long term spectral responsivity, data processing and quality assessment. The cosine correction of the measurements is based on a new method, and included in the data processing software. The results showed that the actual cosine correction factor of the Finnish Brewers can vary between 1.08–1.13 and 1.08–1.12, respectively, depending on the sky radiance distribution and wavelength. The temperature characterization showed a linear temperature dependence between the internal temperature and the photon counts per cycle, and a temperature correction was used for correcting the measurements. The long term spectral responsivity was calculated using time series of several lamps using two slightly different methods. The long term spectral responsivity was scaled to the irradiance scale of the Helsinki University of Technology (HUT) for the whole measurement time periods 1990–2006 and 1995–2006 for Sodankylä and Jokioinen, respectively. Both Brewers have participated in many international spectroradiometer comparisons, and have shown good stability. The differences between the Brewers and the portable reference spectroradiometer QASUME have been within 5% during 2002–2007.

Citation: Lakkala, K., Arola, A., Heikkilä, A., Kaurola, J., Koskela, T., Kyrö, E., Lindfors, A., Meinander, O., Tanskanen, A., Gröbner, J., and Hülsen, G.: Quality assurance of the Brewer UV measurements in Finland, Atmos. Chem. Phys. Discuss., 8, 1415-1455, doi:10.5194/acpd-8-1415-2008, 2008.
 
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