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| Titel |
Indirect radiative forcing by ion-mediated nucleation of aerosol |
| VerfasserIn |
F. Yu, G. Luo, X. Liu, R. C. Easter, X. Ma, S. J. Ghan |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-03), S.11451-11463 |
| Datensatznummer |
250011640
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| Publikation (Nr.) |
 copernicus.org/acp-12-11451-2012.pdf |
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| Zusammenfassung |
| A clear understanding of particle formation mechanisms is
critical for assessing aerosol indirect radiative forcing and associated
climate feedback processes. Recent studies reveal the importance of
ion-mediated nucleation (IMN) in generating new particles and cloud
condensation nuclei (CCN) in the atmosphere. Here we implement the IMN
scheme into the Community Atmosphere Model version 5 (CAM5). Our simulations
show that, compared to globally averaged results based on
H2SO4-H2O binary homogeneous nucleation (BHN), the presence
of ionization (i.e., IMN) halves H2SO4 column burden, but
increases the column integrated nucleation rate by around one order of
magnitude, total particle number burden by a factor of ~3,
CCN burden by ~10% (at 0.2% supersaturation) to 65%
(at 1.0% supersaturation), and cloud droplet number burden by
~18%. Compared to BHN, IMN increases cloud liquid water
path by 7.5%, decreases precipitation by 1.1%, and increases total
cloud cover by 1.9%. This leads to an increase of total shortwave cloud
radiative forcing (SWCF) by 3.67 W m−2 (more negative) and longwave
cloud forcing by 1.78 W m−2 (more positive), with large spatial
variations. The effect of ionization on SWCF derived from this study
(3.67 W m−2) is a factor of ~3 higher that of a previous study
(1.15 W m−2) based on a different ion nucleation scheme and climate
model. Based on the present CAM5 simulation, the 5-yr mean impacts of
solar cycle induced changes in ionization rates on CCN and cloud forcing are
small (~−0.02 W m−2) but have larger inter-annual (from
−0.18 to 0.17 W m−2) and spatial variations. |
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