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Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations

Kylling, A. and Webb, A.R. and Kift, R. and Gobbi, G.P. and Ammannato, L. and Barnaba, F. and Bais, A. and Kadzadzis, S. and Wendisch, M. and Jäkel, E. and Schmidt, S. and Kniffka, A. and Thiel, S. and Junkermann, W. and Blumthaler, M. and Silbernagl, R. and Schallhart, B. and Schmitt, R. and Kjeldstad, B. and Thorseth, T.M. and Scheirer, R. and Mayer, B. (2005) Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations. Atmospheric Chemistry and Physics, 5, pp. 1975-1997.

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Abstract

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.

Document Type:Article
Title:Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations
Authors:
AuthorsInstitution or Email of Authors
Kylling, A.Trondheim Univ. Hospital, N
Webb, A.R.Univ. of Manchester, Manchester, UK
Kift, R.Univ. of Manchester, Manchester, UK
Gobbi, G.P.ISAC-CNR, Roma, I
Ammannato, L.ISAC-CNR, Roma, I
Barnaba, F.ISAC-CNR, Roma, I
Bais, A.Univ. of Thessaloniki, GR
Kadzadzis, S.Univ. of Thessaloniki, GR
Wendisch, M.Leibniz-Inst. für Troposphärenforschung, Leipzig
Jäkel, E.Leibniz-Inst. für Troposphärenforschung, Leipzig
Schmidt, S.Leibniz-Inst. für Troposphärenforschung, Leipzig
Kniffka, A.Univ. Leipzig, Leipzig
Thiel, S.IMK, Garmisch-Partenkirchen
Junkermann, W.IMK, Garmisch-Partenkirchen
Blumthaler, M.Univ. of Innsbruck, Innsbruck, A
Silbernagl, R.Univ. of Innsbruck, Innsbruck, A
Schallhart, B.Univ. of Innsbruck, Innsbruck, A
Schmitt, R.Meteorologie Consult GmbH
Kjeldstad, B.Norwegian Univ. of Science and Technology, Trondheim, N
Thorseth, T.M.Norwegian Univ. of Science and Technology, Trondheim, N
Scheirer, R.UNSPECIFIED
Mayer, B.UNSPECIFIED
Date:2005
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
In Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:5
Page Range:pp. 1975-1997
Status:Published
Keywords:radative transfer, clouds, radiation
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Remote Sensing
Deposited By: Dr.rer.nat. Bernhard Mayer
Deposited On:19 Mar 2007
Last Modified:11 Nov 2014 21:56

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