The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation
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....
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
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| Series: | Annales Geophysicae |
| Online Access: | http://www.ann-geophys.net/14/845/1996/angeo-14-845-1996.html |
| _version_ | 1811248521694674944 |
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| author | P. F. Coley P. R. Jonas |
| author_facet | P. F. Coley P. R. Jonas |
| author_sort | P. F. Coley |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-12T15:29:33Z |
| format | Article |
| id | doaj.art-c4069c30cb404d5ab75093d42b021576 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-12T15:29:33Z |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-c4069c30cb404d5ab75093d42b0215762022-12-22T03:27:10ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-0576148845852The influence of cloud structure and droplet concentration on the reflectance of shortwave radiationP. F. ColeyP. R. JonasThe 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.http://www.ann-geophys.net/14/845/1996/angeo-14-845-1996.html |
| spellingShingle | P. F. Coley P. R. Jonas The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation Annales Geophysicae |
| title | The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| title_full | The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| title_fullStr | The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| title_full_unstemmed | The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| title_short | The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| title_sort | influence of cloud structure and droplet concentration on the reflectance of shortwave radiation |
| url | http://www.ann-geophys.net/14/845/1996/angeo-14-845-1996.html |
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