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| Titel |
Effect of atmospheric gases, surface albedo and cloud overlap on the absorbed solar radiation |
| VerfasserIn |
Ashok Sinha |
| 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. 3 ; Nr. 14, no. 3, S.329-335 |
| Datensatznummer |
250012213
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| Publikation (Nr.) |
 copernicus.org/angeo-14-329-1996.pdf |
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| Zusammenfassung |
| Recent studies have provided new evidence
that models may systematically underestimate cloud solar absorption compared to
observations. This study extends previous work on this "absorption
anomaly'' by using observational data together with solar radiative transfer
parameterisations to calculate fs (the ratio of surface and
top of the atmosphere net cloud forcings) and its latitudinal variation for a
range of cloud types. Principally, it is found that (a) the zonal mean behaviour
of fs varies substantially with cloud type, with the highest
values obtained for low clouds; (b) gaseous absorption and scattering can
radically alter the pattern of the variation of fs with
latitude, but gaseous effects cannot in general raise fs to
the level of around 1.5 as recently determined; (c) the importance of the
gaseous contribution to the atmospheric ASR is such that whilst fs
rises with surface albedo, the net cloud contribution to the atmospheric ASR
falls; (d) the assumed form of the degree of cloud overlap in the model can
substantially affect the cloud contribution to the atmospheric ASR whilst
leaving the parameter fs largely unaffected; (e) even large
uncertainties in the observed optical depths alone cannot account for
discrepancies apparent between modelled and newly observed cloud solar
absorption. It is concluded that the main source of the anomaly may derive from
the considerable uncertainties regarding impure droplet microphysics rather
than, or together with, uncertainties in macroscopic quantities. Further,
variable surface albedos and gaseous effects may limit the use of
contemporaneous satellite and ground-based measurements to infer the cloud solar
absorption from the parameter fs. |
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