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| Titel |
Photolysis frequency measurements aboard Zeppelin NT during PEGASOS 2012/13 |
| VerfasserIn |
Insa Lohse, Birger Bohn, Mathias Bachner, Andreas Hofzumahaus, Frank Holland, Franz Rohrer, Thomas F. Mentel, Astrid Kiendler-Scharr, Andreas Wahner |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095417
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| Publikation (Nr.) |
 EGU/EGU2014-10867.pdf |
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| Zusammenfassung |
| Airborne measurements of the solar spectral actinic flux densities for the determination of
photolysis frequencies in the atmosphere were performed as part of the Pan-European
Gas-AeroSOls-climate interaction Study (PEGASOS). We present the instrumentation and
characterisation of the spectroradiometer systems operated aboard the Zeppelin
NT airship and photolysis frequency data obtained in field campaigns in 2012 and
2013.
Separate measurements of the upwelling and downwelling components of the actinic flux
densities were performed with two instruments covering together a 4Ï-sr field of view. Since
deviations from the ideal 2Ï-sr angular response of each actinic flux receiver can lead to over-
or underestimations of the measured photolysis frequencies, detailed angular sensitivities of
the two optical receivers were determined in the laboratory. The influence of the non-ideal
behaviour on the photolysis frequency measurements was investigated using radiative
transfer calculations of atmospheric radiance distributions under various atmospheric
conditions and different ground albedos. Corresponding correction factor were
derived. This method is also applicable for other research aircraft operating at higher
altitudes.
Measurements of the solar actinic flux densities were performed in the wavelength range
from 280 - 650 nm with a spectral resolution of about 2 nm and averaged over 3 s. An
overview is shown of photolysis frequency data (O3, HNO3, HCHO, H2O2, HNO2, NO2 and
NO3) obtained in the atmospheric boundary layer during the PEGASOS campaigns in the
Netherlands, Italy 2012 and Finland 2013. Dependencies of photolysis frequencies
on cloud cover, flight altitude and wavelength range of the photolysis process are
investigated as well as their influence on the photochemical processing of trace gases.
Moreover the instrumentation allows for estimations of height depending spectral
albedos.
Acknowledgement: Funding by the Deutsche Forschungsgemeinschaft within the
priority program HALO (BO1580/4-1) is gratefully acknowledged. The PEGASOS
project was funded by the European Commission under the Framework Programme 7
(FP7-ENV-2010-265148). |
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