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| Titel |
Modelled radiative forcing of the direct aerosol effect with multi-observation evaluation |
| VerfasserIn |
G. Myhre, T. F. Berglen, M. Johnsrud, C. R. Hoyle, T. K. Berntsen, S. A. Christopher, D. W. Fahey, I. S. A. Isaksen, T. A. Jones, R. A. Kahn, N. Loeb, P. Quinn, L. Remer, J. P. Schwarz, K. E. Yttri |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2009-02-19), S.1365-1392 |
| Datensatznummer |
250006932
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| Publikation (Nr.) |
 copernicus.org/acp-9-1365-2009.pdf |
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| Zusammenfassung |
| A high-resolution global aerosol model (Oslo CTM2) driven by meteorological
data and allowing a comparison with a variety of aerosol observations is
used to simulate radiative forcing (RF) of the direct aerosol effect. The
model simulates all main aerosol components, including several secondary
components such as nitrate and secondary organic carbon. The model
reproduces the main chemical composition and size features observed during
large aerosol campaigns. Although the chemical composition compares best
with ground-based measurement over land for modelled sulphate, no systematic
differences are found for other compounds. The modelled aerosol optical
depth (AOD) is compared to remote sensed data from AERONET ground and MODIS
and MISR satellite retrievals. To gain confidence in the aerosol modelling,
we have tested its ability to reproduce daily variability in the aerosol
content, and this is performing well in many regions; however, we also
identified some locations where model improvements are needed. The annual
mean regional pattern of AOD from the aerosol model is broadly similar to
the AERONET and the satellite retrievals (mostly within 10–20%). We
notice a significant improvement from MODIS Collection 4 to Collection 5
compared to AERONET data. Satellite derived estimates of aerosol radiative
effect over ocean for clear sky conditions differs significantly on regional
scales (almost up to a factor two), but also in the global mean. The Oslo
CTM2 has an aerosol radiative effect close to the mean of the satellite
derived estimates. We derive a radiative forcing (RF) of the direct aerosol
effect of −0.35 Wm−2 in our base case. Implementation of a simple
approach to consider internal black carbon (BC) mixture results in a total
RF of −0.28 Wm−2. Our results highlight the importance of carbonaceous
particles, producing stronger individual RF than considered in the recent
IPCC estimate; however, net RF is less different. A significant RF from
secondary organic aerosols (SOA) is estimated (close to −0.1 Wm−2). The
SOA also contributes to a strong domination of secondary aerosol species for
the aerosol composition over land. A combination of sensitivity simulations
and model evaluation show that the RF is rather robust and unlikely to be
much stronger than in our best estimate. |
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