We present three different methods for the absolute calibration of direct spectral irradiances measured with a Brewer spectroradiometer, which are shown to agree to within ±2%. Direct irradiance spectra derived by Brewer and Bentham spectroradiometers agree to within 4 ± 3%. Good agreement was also found by a comparison of the aerosol optical depth and Angstrom exponent retrieved by the two instruments and a multifilter rotational shadowband radiometer.
The spectral aerosol optical depth (300–365 nm) derived from six years of direct irradiance measurements at Thessaloniki shows a distinct seasonal variation, averaging to ~0.3 at 340 nm in winter and ~0.7 in summer.
© 2005 Optical Society of America
Kazadzis, S., Bais, A., Kouremeti, N., Gerasopoulos, E., Garane, K., Blumthaler, M., Schallhart, B. and Cede, A., 2005. Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval. Applied optics, 44(9), pp.1681-1690.
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