Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval.
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.
Kazadzis
Stelios
S
Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, P.O. Box 149, Thessaloniki 54124, Greece. skaza@skiathos.physics.auth.gr
Bais
Alkiviadis
A
Kouremeti
Natalia
N
Gerasopoulos
Evangelos
E
Garane
Katerina
K
Blumthaler
Mario
M
Schallhart
Barbara
B
Cede
Alexander
A