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| Titel |
Host model uncertainties in aerosol radiative forcing estimates: results from the AeroCom Prescribed intercomparison study |
| VerfasserIn |
P. Stier, N. A. J. Schutgens, N. Bellouin, H. Bian, O. Boucher, M. Chin, S. Ghan, N. Huneeus, S. Kinne, G. Lin, X. Ma, G. Myhre, J. E. Penner, C. A. Randles, B. Samset, M. Schulz, T. Takemura, F. Yu, H. Yu, C. Zhou |
| 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 ; 13, no. 6 ; Nr. 13, no. 6 (2013-03-20), S.3245-3270 |
| Datensatznummer |
250018531
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| Publikation (Nr.) |
 copernicus.org/acp-13-3245-2013.pdf |
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| Zusammenfassung |
Simulated multi-model "diversity" in aerosol direct radiative forcing
estimates is often perceived as a measure of aerosol uncertainty. However,
current models used for aerosol radiative forcing calculations vary
considerably in model components relevant for forcing calculations and the
associated "host-model uncertainties" are generally convoluted with the
actual aerosol uncertainty. In this AeroCom Prescribed intercomparison study
we systematically isolate and quantify host model uncertainties on aerosol
forcing experiments through prescription of identical aerosol radiative
properties in twelve participating models.
Even with prescribed aerosol radiative properties, simulated clear-sky and
all-sky aerosol radiative forcings show significant diversity. For a purely
scattering case with globally constant optical depth of 0.2, the global-mean
all-sky top-of-atmosphere radiative forcing is −4.47 Wm−2 and the
inter-model standard deviation is 0.55 Wm−2, corresponding to a
relative standard deviation of 12%. For a case with partially absorbing
aerosol with an aerosol optical depth of 0.2 and single scattering albedo of
0.8, the forcing changes to 1.04 Wm−2, and the standard deviation
increases to 1.01 W−2, corresponding to a significant relative standard
deviation of 97%. However, the top-of-atmosphere forcing variability owing
to absorption (subtracting the scattering case from the case with scattering
and absorption) is low, with absolute (relative) standard deviations of
0.45 Wm−2 (8%) clear-sky and 0.62 Wm−2 (11%) all-sky.
Scaling the forcing standard deviation for a purely scattering case to match
the sulfate radiative forcing in the AeroCom Direct Effect experiment
demonstrates that host model uncertainties could explain about 36% of
the overall sulfate forcing diversity of 0.11 Wm−2 in the AeroCom
Direct Radiative Effect experiment.
Host model errors in aerosol radiative forcing are largest in regions
of uncertain host model components, such as stratocumulus cloud decks
or areas with poorly constrained surface albedos, such as sea ice.
Our results demonstrate that host model uncertainties are an
important component of aerosol forcing uncertainty that require further attention. |
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