A description of the global sulfur cycle and its controlling processes in the National Center for Atmospheric Research Community Climate Model, Version 3

Abstract

-cloud), and type of emissions (anthropogenic versus biogenic) is used to differentiate the balance of processes controlling the production and loading from this material. Significant differences exist in the destiny of SO2 molecules emitted from the several regions. An SO2 molecule emitted from the ROW source region has a much greater potential to form sulfate than one emitted from, for example, Europe. A greater fraction of the SO2 molecules is oxidized that originate from ROW compared with other areas, and once formed, the sulfate has a longer residence time (that is, it is not readily scavenged). The yield of sulfate from ROW sources of SO2 is a factor of 4 higher than that of Europe. A substantially higher fraction of the SO2 emitted over Europe is oxidized to sulfate through the ozone pathway compared to other regions. The analysis suggests that there are significant differences in the vertical distribution, and horizontal extent, of the propagation of sulfate emitted from the several source regions. Sulfate from Asian source regions reaches the farthest from its point of origin and makes a significant contribution to burdens in both hemispheres, primarily from plumes reaching out in the upper troposphere. Sulfate from other source regions tends to remain trapped in their hemisphere of origin.

Variable CCN formation potential of regional sulfur emissions

“…The fraction of SO 2 converted into SO 4 (sulfate production efficiency) lies in the range 0.38-0.51 and, consistent with previous studies, is lowest for W. Europe (Chin et al, 2000;Rasch et al, 2000;Koch et al, 2007;Manktelow et al, 2007) where SO 2 deposition is favored by the slow venting of the boundary layer and where oxidants are more limited than at lower latitudes. The contribution of each region to total (anthropogenic + natural) global SO 4 (SO 4glob ) can be expressed as a fraction of the contribution to total global sulfur emissions, giving a sulfate burden potential (Rasch et al, 2000): (1) where i is the grid box index and reg implies SO 4 originating from regional anthropogenic SO 2 . In our model for the year 2000 European SO 4 has the longest lifetime (due to slow wet deposition), giving Europe a sulfate burden potential 57% and 4% larger than E. Asia and N. America, respectively.…”

“…In our model for the year 2000 European SO 4 has the longest lifetime (due to slow wet deposition), giving Europe a sulfate burden potential 57% and 4% larger than E. Asia and N. America, respectively. In contrast, Rasch et al (2000) found that Asia had the largest sulfate burden potential, while Koch et al (2007) found N. America to be the most efficient source. These intermodel differences may be largely attributable to differences in the setup of each model experiment.…”

“…Although there are inter-model differences (Rasch et al (2000) identified E. Asia as the most efficient source, while Koch et al (2007) found N. America to be most efficient) these studies suggest that the climate forcing potential of SO 2 depends on where the gas is emitted. In the Koch et al (2007) study the aerosol direct forcing potential of the regional emissions was found to be very similar to the sulfate burden potential.…”

“…These intermodel differences may be largely attributable to differences in the setup of each model experiment. Our anthropogenic SO 2 emissions are derived from the AEROCOM 2000 inventory (Cofala et al, 2005), while Rasch et al (2000) used the earlier GEIA 1B 1985 emissions (Benkovitz et al, 1996) and Koch et al (2007) used EDGAR 3.2 1995(Olivier and Berdowski, 2001). There are considerable differences in the magnitude of SO 2 emission over Europe, N. America and Asia between each inventory, which will have a significant influence on the behavior of sulfur emitted from each region (Manktelow et al, 2007).…”

“…Model studies (Rasch et al, 2000;Koch et al, 2007) have found that the potential of anthropogenic SO 2 emissions to generate sulfate mass varies by a factor of 2 between E. Asia, N. America and Europe because of regional differences in these meteorological and chemical processes. Although there are inter-model differences (Rasch et al (2000) identified E. Asia as the most efficient source, while Koch et al (2007) found N. America to be most efficient) these studies suggest that the climate forcing potential of SO 2 depends on where the gas is emitted.…”