Kazadzis Stelios, Bais Alkiviadis, Kouremeti Natalia, Gerasopoulos Evangelos, Garane Katerina, Blumthaler Mario, Schallhart Barbara, Cede Alexander
Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, P.O. Box 149, Thessaloniki 54124, Greece.
Appl Opt. 2005 Mar 20;44(9):1681-90. doi: 10.1364/ao.44.001681.
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 approximately 0.3 at 340 nm in winter and approximately 0.7 in summer.
