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| Titel |
Climate response due to carbonaceous aerosols and aerosol-induced SST effects in NCAR community atmospheric model CAM3.5 |
| VerfasserIn |
W.-C. Hsieh, W. D. Collins, Y. Liu, J. C. H. Chiang, C.-L. Shie, K. Caldeira, L. Cao |
| 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. 15 ; Nr. 13, no. 15 (2013-08-05), S.7489-7510 |
| Datensatznummer |
250085606
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| Publikation (Nr.) |
 copernicus.org/acp-13-7489-2013.pdf |
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| Zusammenfassung |
| This study used the Community Atmospheric Model 3.5 (CAM3.5) to investigate the
effects of carbonaceous aerosols on climate. The simulations include control
runs with 3 times the mass of carbonaceous aerosols as compared to the
model's default carbonaceous aerosol mass, as well as no-carbon runs in which
carbonaceous aerosols were removed. The slab ocean model (SOM) and the fixed
sea surface temperature (SST) were used to examine effects of ocean boundary
conditions. Throughout this study, climate response induced by aerosol
forcing was mainly analyzed in the following three terms: (1) aerosol
radiative effects under fixed SST, (2) effects of aerosol-induced SST
feedbacks, and (3) total effects including effects of aerosol forcing and SST
feedbacks. The change of SST induced by aerosols has large impacts on
distribution of climate response; the magnitudes in response patterns such as
temperature, precipitation, zonal winds, mean meridional circulation,
radiative fluxes, and cloud coverage are different between the SOM and fixed
SST runs. Moreover, different spatial responses between the SOM and fixed SST
runs can also be seen in some local areas. This implies the importance of SST
feedbacks on simulated climate response. The aerosol dimming effects cause
a cooling predicted at low layers near the surface in most carbonaceous
aerosol source regions. The temperature response shows a warming (cooling)
predicted in the north (south) high latitudes, suggesting that aerosol
forcing can cause climate change in regions far away from its origins. Our
simulation results show that direct and semidirect radiative forcing due to
carbonaceous aerosols decreases rainfall in the tropics. This implies that
carbonaceous aerosols have possibly strong influence on weakening of the
tropical circulation. Most changes in precipitation are negatively
correlated with changes of radiative fluxes at the top of model. The changes
in radiative fluxes at top of model are physically consistent with the
response patterns in cloud fields. On global average, low-level cloud
coverage increases, and mid- and high-level cloud coverage decreases in response
to changes in radiative energy induced by aerosol forcing. An approximated
moisture budget equation was analyzed in order to understand physical
mechanism of precipitation changes induced by carbonaceous aerosols. Our
results show that changes in tropical precipitation are mainly dominated are mainly dominated by the dynamic effect (i.e., vertical moisture transport carried by the perturbed
flow). |
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