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| Titel |
Estimating the direct and indirect effects of secondary organic aerosols using ECHAM5-HAM |
| VerfasserIn |
D. O'Donnell, K. Tsigaridis, J. Feichter |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-25), S.8635-8659 |
| Datensatznummer |
250010027
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| Publikation (Nr.) |
 copernicus.org/acp-11-8635-2011.pdf |
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| Zusammenfassung |
| Secondary organic aerosol (SOA) has been introduced into the global
climate-aerosol model ECHAM5/HAM. The SOA module handles aerosols
originating from both biogenic and anthropogenic sources. The model
simulates the emission of precursor gases, their chemical conversion into
condensable gases, the partitioning of semi-volatile condenable species into
the gas and aerosol phases. As ECHAM5/HAM is a size-resolved model, a new
method that permits the calculation of partitioning of semi-volatile species
between different size classes is introduced. We compare results of modelled
organic aerosol concentrations against measurements from extensive
measurement networks in Europe and the United States, running the model with
and without SOA. We also compare modelled aerosol optical depth against
measurements from the AERONET network of grond stations. We find that SOA
improves agreement between model and measurements in both organic aerosol
mass and aerosol optical depth, but does not fully correct the low bias that
is present in the model for both of these quantities. Although many models
now include SOA, any overall estimate of the direct and indirect effects of
these aerosols is still lacking. This paper makes a first step in that
direction. The model is applied to estimate the direct and indirect effects
of SOA under simulated year 2000 conditions. The modelled SOA spatial
distribution indicates that SOA is likely to be an important source of free
and upper tropospheric aerosol. We find a negative shortwave (SW) forcing
from the direct effect, amounting to −0.31 Wm−2 on the global
annual mean. In contrast, the model indicates a positive indirect effect of
SOA of +0.23 Wm−2, arising from the enlargement of particles due to
condensation of SOA, together with an enhanced coagulation sink of small
particles. In the longwave, model results are a direct effect of
+0.02 Wm−2 and an indirect effect of −0.03 Wm−2. |
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