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| Titel |
Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment |
| VerfasserIn |
H. Guo, J. E. Penner, M. Herzog, H. Pawlowska |
| 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 ; 7, no. 2 ; Nr. 7, no. 2 (2007-01-29), S.535-548 |
| Datensatznummer |
250004476
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| Publikation (Nr.) |
 copernicus.org/acp-7-535-2007.pdf |
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| Zusammenfassung |
The Active Tracer High-resolution Atmospheric Model (ATHAM) has been adopted
to examine the aerosol indirect effect in contrasting clean and polluted
cloudy boundary layers during the Second Aerosol Characterization Experiment
(ACE-2). Model results are in good agreement with available in-situ
observations, which provides confidence in the results of ATHAM.
Sensitivity tests have been conducted to examine the response of the cloud
fraction (CF), cloud liquid water path (LWP), and cloud optical depth (COD)
to changes in aerosols in the clean and polluted cases. It is shown for two
cases that CF and LWP would decrease or remain nearly constant with an
increase in aerosols, a result which shows that the second aerosol indirect
effect is positive or negligibly small in these cases. Further investigation indicates that the
background meteorological conditions play a critical role in the response of
CF and LWP to aerosols. When large-scale subsidence is weak as in the clean
case, the dry overlying air above the cloud is more efficiently entrained
into the cloud, and in so doing, removes cloud water more efficiently, and
results in lower CF and LWP when aerosol burden increases. However, when the
large-scale subsidence is strong as in the polluted case, the growth of the
cloud top is suppressed and the entrainment drying makes no significant
difference when aerosol burden increases. Therefore, the CF and LWP remain
nearly constant.
In both the clean and polluted cases, the COD tends to increase with
aerosols, and the total aerosol indirect effect (AIE) is negative even when
the CF and LWP decrease with an increase in aerosols. Therefore, the
first AIE dominates the response of the cloud to aerosols. |
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