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| Titel |
A new method for the absolute radiance calibration for UV–vis measurements of scattered sunlight |
| VerfasserIn |
T. Wagner, S. Beirle, S. Dörner, M. Penning de Vries, J. Remmers, A. Rozanov, R. Shaiganfar |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 10 ; Nr. 8, no. 10 (2015-10-14), S.4265-4280 |
| Datensatznummer |
250116637
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| Publikation (Nr.) |
 copernicus.org/amt-8-4265-2015.pdf |
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| Zusammenfassung |
| Absolute radiometric calibrations are important for
measurements of the atmospheric spectral radiance. Such measurements can be
used to determine actinic fluxes, the properties of aerosols and clouds, and
the shortwave energy budget. Conventional calibration methods in the
laboratory are based on calibrated light sources and reflectors and are
expensive, time consuming and subject to relatively large uncertainties.
Also, the calibrated instruments might change during transport from the
laboratory to the measurement sites. Here we present a new calibration
method for UV–vis instruments that measure the spectrally resolved sky
radiance, for example zenith sky differential optical absorption
spectroscopy (DOAS) instruments or multi-axis (MAX)-DOAS instruments. Our
method is based on the comparison of the solar zenith angle dependence of
the measured zenith sky radiance with radiative transfer simulations. For
the application of our method, clear-sky measurements during periods with
almost constant aerosol optical depth are needed. The radiative transfer
simulations have to take polarisation into account. We show that the
calibration results are almost independent from the knowledge of the aerosol
optical properties and surface albedo, which causes a rather small
uncertainty of about < 7 %. For wavelengths below about 330 nm
it is essential that the ozone column density during the measurements be
constant and known. |
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