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| Titel |
Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations |
| VerfasserIn |
A. Kylling, A. R. Webb, R. Kift, G. P. Gobbi, L. Ammannato, F. Barnaba, A. Bais, S. Kazadzis, M. Wendisch, E. Jäkel, S. Schmidt, A. Kniffka, S. Thiel, W. Junkermann, M. Blumthaler, R. Silbernagl, B. Schallhart, R. Schmitt, B. Kjeldstad, T. M. Thorseth, R. Scheirer, B. Mayer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 5, no. 7 ; Nr. 5, no. 7 (2005-08-03), S.1975-1997 |
| Datensatznummer |
250002994
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| Publikation (Nr.) |
 copernicus.org/acp-5-1975-2005.pdf |
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| Zusammenfassung |
| In September 2002, the first INSPECTRO campaign to study the influence of
clouds on the spectral actinic flux in the lower troposphere was
carried out in East Anglia, England. Measurements of the actinic flux,
the irradiance and aerosol and cloud properties were made from four
ground stations and by aircraft. The radiation measurements were
modelled using the uvspec model and ancillary data.
For cloudless conditions, the measurements of the actinic flux were
reproduced by 1-D radiative transfer modelling within the measurement and model
uncertainties of about ±10%.
For overcast days, the ground-based and aircraft radiation
measurements and the cloud microphysical property measurements are
consistent within the framework of 1-D radiative transfer and within
experimental uncertainties. Furthermore,
the actinic flux is increased by between 60-100% above the cloud when compared
to a cloudless sky, with the largest increase for the optically
thickest cloud. Correspondingly, the below cloud actinic flux is decreased by
about 55-65%. Just below the cloud top, the downwelling actinic
flux has a maximum that is seen in both the measurements and the
model results.
For broken clouds the traditional cloud fraction approximation is not
able to simultaneously reproduce the measured above-cloud enhancement
and below-cloud reduction in the actinic flux. |
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