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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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Atmos. Meas. Tech., 7, 2137-2146, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
16 Jul 2014
Validation of spectral sky radiance derived from all-sky camera images – a case study
K. Tohsing, M. Schrempf, S. Riechelmann, and G. Seckmeyer Institut für Meteorologie und Klimatologie, Leibniz Universität Hannover, Herrenhäuser Straße 2, Hanover 30419, Germany
Abstract. Spectral sky radiance (380–760 nm) is derived from measurements with a hemispherical sky imager (HSI) system. The HSI consists of a commercial compact CCD (charge coupled device) camera equipped with a fish-eye lens and provides hemispherical sky images in three reference bands such as red, green and blue. To obtain the spectral sky radiance from these images, non-linear regression functions for various sky conditions have been derived. The camera-based spectral sky radiance was validated using spectral sky radiance measured with a CCD spectroradiometer. The spectral sky radiance for complete distribution over the hemisphere between both instruments deviates by less than 20% at 500 nm for all sky conditions and for zenith angles less than 80°. The reconstructed spectra of the wavelengths 380–760 nm between both instruments at various directions deviate by less than 20% for all sky conditions.

Citation: Tohsing, K., Schrempf, M., Riechelmann, S., and Seckmeyer, G.: Validation of spectral sky radiance derived from all-sky camera images – a case study, Atmos. Meas. Tech., 7, 2137-2146,, 2014.
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