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| Titel |
The multi-scale aerosol-climate model PNNL-MMF: model description and evaluation |
| VerfasserIn |
M. Wang, S. Ghan, R. Easter, M. Ovchinnikov, X. Liu, E. Kassianov, Y. Qian, W. I. Jr. Gustafson, V. E. Larson, D. P. Schanen, M. Khairoutdinov, H. Morrison |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 4, no. 1 ; Nr. 4, no. 1 (2011-03-03), S.137-168 |
| Datensatznummer |
250001558
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| Publikation (Nr.) |
 copernicus.org/gmd-4-137-2011.pdf |
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| Zusammenfassung |
Anthropogenic aerosol effects on climate produce one of the largest
uncertainties in estimates of radiative forcing of past and future climate
change. Much of this uncertainty arises from the multi-scale nature of the
interactions between aerosols, clouds and large-scale dynamics, which are
difficult to represent in conventional general circulation models (GCMs). In
this study, we develop a multi-scale aerosol-climate model that treats
aerosols and clouds across different scales, and evaluate the model
performance, with a focus on aerosol treatment. This new model is an
extension of a multi-scale modeling framework (MMF) model that embeds a
cloud-resolving model (CRM) within each grid column of a GCM. In this
extension, the effects of clouds on aerosols are treated by using an
explicit-cloud parameterized-pollutant (ECPP) approach that links aerosol and
chemical processes on the large-scale grid with statistics of cloud
properties and processes resolved by the CRM. A two-moment cloud microphysics
scheme replaces the simple bulk microphysics scheme in the CRM, and a modal
aerosol treatment is included in the GCM. With these extensions, this
multi-scale aerosol-climate model allows the explicit simulation of aerosol
and chemical processes in both stratiform and convective clouds on a global
scale.
Simulated aerosol budgets in this new model are in the ranges of other model
studies. Simulated gas and aerosol concentrations are in reasonable agreement
with observations (within a factor of 2 in most cases), although the model
underestimates black carbon concentrations at the surface by a factor of
2–4. Simulated aerosol size distributions are in reasonable agreement with
observations in the marine boundary layer and in the free troposphere, while
the model underestimates the accumulation mode number concentrations near the
surface, and overestimates the accumulation mode number concentrations in the
middle and upper free troposphere by a factor of about 2. The overestimation
of accumulation model number concentrations in the middle and upper free
troposphere is consistent with large aerosol mass fraction above 5 km in the
MMF model compared with other models. Simulated cloud condensation nuclei
(CCN) concentrations are within the observational variations. Simulated
aerosol optical depths (AOD) are in reasonable agreement with observations
(within a factor of 2), and the spatial distribution of AOD is consistent
with observations, while the model underestimates AOD over regions with
strong fossil fuel and biomass burning emissions. Overall, this multi-scale
aerosol-climate model simulates aerosol fields as well as conventional
aerosol models. |
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