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| Titel |
The impact of cloud inhomogeneities on the Earth radiation budget: the 14 October 1989 I.C.E. convective cloud case study |
| VerfasserIn |
F. Parol, J. C. Buriez, D. Crétel, Y. Fouquart |
| 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 ; 12, no. 2/3 ; Nr. 12, no. 2/3, S.240-253 |
| Datensatznummer |
250010326
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| Publikation (Nr.) |
 copernicus.org/angeo-12-240-1994.pdf |
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| Zusammenfassung |
| Through their multiple interactions with
radiation, clouds have an important impact on the climate. Nonetheless, the
simulation of clouds in climate models is still coarse. The present evolution of
modeling tends to a more realistic representation of the liquid water content;
thus the problem of its subgrid scale distribution is crucial. For a convective
cloud field observed during ICE 89, Landsat TM data (resolution: 30m) have been
analyzed in order to quantify the respective influences of both the horizontal
distribution of liquid water content and cloud shape on the Earth radiation
budget. The cloud field was found to be rather well-represented by a stochastic
distribution of hemi-ellipsoidal clouds whose horizontal aspect ratio is close
to 2 and whose vertical aspect ratio decreases as the cloud cell area increases.
For that particular cloud field, neglecting the influence of the cloud shape
leads to an over-estimate of the outgoing longwave flux; in the shortwave, it
leads to an over-estimate of the reflected flux for high solar elevations but
strongly depends on cloud cell orientations for low elevations. On the other
hand, neglecting the influence of cloud size distribution leads to systematic
over-estimate of their impact on the shortwave radiation whereas the effect is
close to zero in the thermal range. The overall effect of the heterogeneities is
estimated to be of the order of 10 W m-2 for the conditions of that
Landsat picture (solar zenith angle 65°, cloud cover 70%); it might reach 40 W
m-2 for an overhead sun and overcast cloud conditions. |
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