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
(010.1110) Atmospheric and oceanic optics : Aerosols
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
Stelios Kazadzis, Alkiviadis Bais, Natalia Kouremeti, Evangelos Gerasopoulos, Katerina Garane, Mario Blumthaler, Barbara Schallhart, and Alexander Cede, "Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval," Appl. Opt. 44, 1681-1690 (2005)