Yu, H., Chin, M., West, J. J., Atherton, C. S., Bellouin, N., Bergmann, D., Bey, I., Bian, H., Diehl, T., Forberth, G., Hess, P., Schulz, M., Shindell, D., Takemura, T. and Tan, Q.
A multimodel assessment of the influence of regional anthropogenic emission reductions on aerosol direct radiative forcing and the role of intercontinental transport.
Journal of Geophysical Research: Atmospheres, 118 (2).
To link to this article DOI: 10.1029/2012JD018148
In this study, we assess changes of aerosol optical depth (AOD) and direct radiative
forcing (DRF) in response to the reduction of anthropogenic emissions in four major
pollution regions in the Northern Hemisphere by using results from nine global models in
the framework of the Hemispheric Transport of Air Pollution (HTAP). DRF at top of
atmosphere (TOA) and surface is estimated based on AOD results from the HTAP models
and AOD-normalized DRF (NDRF) from a chemical transport model. The multimodel
results show that, on average, a 20% reduction of anthropogenic emissions in North
America, Europe, East Asia, and South Asia lowers the global mean AOD (all-sky TOA
DRF) by 9.2% (9.0%), 3.5% (3.0%), and 9.4% (10.0%) for sulfate, particulate organic
matter (POM), and black carbon (BC), respectively. Global annual average TOA all-sky
forcing efficiency relative to particle or gaseous precursor emissions from the four regions
(expressed as multimodel mean ± one standard deviation) is ±3.5 ±0.8, ±4.0 ±1.7, and
29.5 ±18.1mWm ±2 per Tg for sulfate (relative to SO2), POM, and BC, respectively. The
impacts of the regional emission reductions on AOD and DRF extend well beyond the
source regions because of intercontinental transport (ICT). On an annual basis, ICT
accounts for 11 ±5% to 31 ±9% of AOD and DRF in a receptor region at continental or
subcontinental scale, with domestic emissions accounting for the remainder, depending on
regions and species. For sulfate AOD, the largest ICT contribution of 31 ±9% occurs in
South Asia, which is dominated by the emissions from Europe. For BC AOD, the largest
ICT contribution of 28 ±18% occurs in North America, which is dominated by the
emissions from East Asia. The large spreads among models highlight the need to improve
aerosol processes in models, and evaluate and constrain models with observations.
|Date Deposited:||31 Oct 2013 13:13|
|Last Modified:||07 Dec 2016 03:07|
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