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dc.contributor.author
Quaas, Johannes
dc.contributor.author
Ming, Y.
dc.contributor.author
Menon, Surabi
dc.contributor.author
Takemura, Toshihiko
dc.contributor.author
Wang, M.
dc.contributor.author
Penner, Joyce E.
dc.contributor.author
Gettelman, Andrew
dc.contributor.author
Lohmann, Ulrike
dc.contributor.author
Bellouin, Nicolas
dc.contributor.author
Boucher, Olivier
dc.contributor.author
Sayer, Andrew M.
dc.contributor.author
Thomas, G.E.
dc.contributor.author
McComiskey, Allison
dc.contributor.author
Feingold, Graham
dc.contributor.author
Hoose, C.
dc.contributor.author
Kristjánsson, Jón E.
dc.contributor.author
Liu, X.
dc.contributor.author
Balkanski, Yves
dc.contributor.author
Donner, Leo J.
dc.contributor.author
Ginoux, Paul A.
dc.contributor.author
Stier, Philip
dc.contributor.author
Grandey, Benjamin
dc.contributor.author
Feichter, Johann
dc.contributor.author
Sednev, Igor
dc.contributor.author
Bauer, Susanne E.
dc.contributor.author
Koch, Dorothy
dc.contributor.author
Grainger, Roy G.
dc.contributor.author
Kirkevåg, Alf
dc.contributor.author
Iversen, Trond
dc.contributor.author
Seland, Øyvind
dc.contributor.author
Easter, Richard
dc.contributor.author
Ghan, Steven J.
dc.contributor.author
Rasch, Phil J.
dc.contributor.author
Morrison, Hugh
dc.contributor.author
Lamarque, Jean-François
dc.contributor.author
Iacono, Michael J.
dc.contributor.author
Kinne, Stefan
dc.contributor.author
Schulz, M.
dc.date.accessioned
2018-10-02T12:56:28Z
dc.date.available
2017-06-11T08:07:44Z
dc.date.available
2017-10-26T11:48:25Z
dc.date.available
2018-10-02T12:56:28Z
dc.date.issued
2009
dc.identifier.issn
1680-7375
dc.identifier.issn
1680-7367
dc.identifier.other
10.5194/acp-9-8697-2009
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/83786
dc.identifier.doi
10.3929/ethz-b-000083786
dc.description.abstract
Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–τa relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR–τa relationship show a strong positive correlation between τa and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrieved Nd–τa regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2 Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm−2, with a total estimate of −1.2±0.4 Wm−2.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
Copernicus
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/3.0/
dc.title
Aerosol indirect effects - general circulation model intercomparison and evaluation with satellite data
en_US
dc.type
Journal Article
dc.rights.license
Creative Commons Attribution 3.0 Unported
dc.date.published
2009-11-16
ethz.journal.title
Atmospheric Chemistry and Physics
ethz.journal.volume
9
en_US
ethz.journal.issue
22
en_US
ethz.journal.abbreviated
Atmos. chem. phys.
ethz.pages.start
8697
en_US
ethz.pages.end
8717
en_US
ethz.version.deposit
publishedVersion
en_US
ethz.identifier.wos
ethz.identifier.nebis
004294181
ethz.publication.place
Göttingen
en_US
ethz.publication.status
published
en_US
ethz.date.deposited
2017-06-11T08:10:26Z
ethz.source
ECIT
ethz.identifier.importid
imp593651df6173d15245
ethz.ecitpid
pub:132128
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2017-07-12T22:17:46Z
ethz.rosetta.lastUpdated
2018-10-02T12:56:34Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
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