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| Titel |
Thunderstorm and stratocumulus: how does their contrasting morphology affect their interactions with aerosols? |
| VerfasserIn |
S. S. Lee, L. J. Donner, J. E. Penner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 14 ; Nr. 10, no. 14 (2010-07-23), S.6819-6837 |
| Datensatznummer |
250008656
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| Publikation (Nr.) |
 copernicus.org/acp-10-6819-2010.pdf |
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| Zusammenfassung |
| It is well-known that aerosols affect clouds and that the effect of aerosols
on clouds is critical for understanding human-induced climate change. Most
climate model studies have focused on the effect of aerosols on warm
stratiform clouds (e.g., stratocumulus clouds) for the prediction of climate
change. However, systems like the Asian and Indian Monsoon, storm tracks,
and the intertropical convergence zone, play important roles in the global
hydrological cycle and in the circulation of energy and are driven by
thunderstorm-type convective clouds. Here, we show that the different
morphologies of these two cloud types lead to different aerosol-cloud
interactions. Increasing aerosols are known to suppress the conversion of
droplets to rain (i.e., so-called autoconversion). This increases droplets
as a source of evaporative cooling, leading to an increased intensity of
downdrafts. The acceleration of the intensity of downdrafts is larger in
convective clouds due to their larger cloud depths (providing longer paths
for downdrafts to follow to the surface) than in stratiform clouds. More
accelerated downdrafts intensify the gust front, leading to significantly
increased updrafts, condensation and thus the collection of cloud liquid by
precipitation, which offsets the suppressed autoconversion. This leads to an
enhancement of precipitation with increased aerosols in convective clouds.
However, the downdrafts are less accelerated in stratiform clouds due to
their smaller cloud depths, and they are not able to induce changes in
updrafts as large as those in convective clouds. Thus, the offset is not as
effective, and this allows the suppression of precipitation with increased
aerosols. Thus aerosols affect these cloud systems differently. The
dependence of the effect of aerosols on clouds on the morphology of clouds
should be taken into account for a more complete assessment of climate
change. |
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