Publication Date:
2014-11-28
Description:
The global atmospheric sulfur budget and its emission dependence have been investigated using the coupled aerosol-chemistry climate model SOCOL-AER. The aerosol module comprises gaseous and aqueous sulfur chemistry and comprehensive microphysics. The particle distribution is resolved by 40 size bins spanning radii from 0.39 nm to 3.2 μ m, including size-dependent particle composition. Aerosol radiative properties required by the climate model are calculated online from the aerosol module. The model successfully reproduces main features of stratospheric aerosols under non-volcanic conditions, including aerosol extinctions compared to SAGE-II and HALOE, and size distributions compared to in situ measurements. The calculated stratospheric aerosol burden is 109 Gg of sulfur, matching the SAGE-II-based estimate (112 Gg). In terms of fluxes through the tropopause, the stratospheric aerosol layer is due to about 43% primary tropospheric aerosol, 28% SO 2 , 23% OCS, 4% H 2 S and 2% DMS. Turning off emissions of the short-lived species SO 2 , H 2 S and DMS shows that OCS alone still establishes about 56% of the original stratospheric aerosol burden. Further sensitivity simulations reveal that anticipated increases in anthropogenic SO 2 emissions in China and India have a larger influence on stratospheric aerosols than the same increase in Western Europe or the US, due to deep convection in the Western Pacific region. However, even a doubling of Chinese and Indian emissions is predicted to increase the stratospheric background aerosol burden only by 9%. In contrast, small to moderate volcanic eruptions, such as that of Nabro in 2011, may easily double the stratospheric aerosol loading.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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