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| Titel |
The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| VerfasserIn |
P. F. Coley, P. R. Jonas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 8 ; Nr. 14, no. 8, S.845-852 |
| Datensatznummer |
250012388
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| Publikation (Nr.) |
 copernicus.org/angeo-14-845-1996.pdf |
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| Zusammenfassung |
| The effects of cloud shadowing, channelling,
cloud side illumination and droplet concentration are investigated with regard
to the reflection of shortwave solar radiation. Using simple geometric clouds,
coupled with a Monte Carlo model the transmission properties of idealized cloud
layers are found. The clouds are illuminated with direct solar radiation from
above. The main conclusion reached is that the distribution of the cloud has a
very large influence on the reflectivity of a cloud layer. In particular, if the
cloud contains vertical gaps through the cloud layer in which the liquid water
content is zero, then, smaller more numerous gaps are more influential on the
radiation than fewer, larger gaps with equal cloud fraction. At very low solar
zenith angles channelling of the radiation reduces the reflection expected on
the basis of the percentage cloud cover. At high solar zenith angles the
illumination of the cloud edges significantly increases the reflection despite
the shadowing of one cloud by another when the width of the gaps is small. The
impact of droplet concentration upon the reflection of cloud layers is also
investigated. It is found that at low solar zenith angles where channelling is
important, the lower concentrations increase the transmission. Conversely, when
cloud edge illumination is dominant the cloud distribution is found to be more
important for the higher concentrations. |
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