05 September 2017

Sourcing Sulfate and its Effect on Earth’s Energy Balance

Scientists found that over regions with relatively low sulfur release, near-surface sulfate concentrations primarily come from afar.

Science

Atmospheric sulfate particles come from sources all over the world. These particles influence Earth’s energy balance—radiative forcing—directly through scattering sunlight and indirectly through modifying cloud microphysical properties, and contribute to poor air quality in many areas of the globe. A study led by scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory revealed the quantitative influence of sulfur release from 16 source regions/sectors on regional energy balance and poor air quality in many regions. Scientists also examined the transport pathways between source and receptor regions.

Impact

Researchers found that dimethyl sulfide from oceans contributed the most to direct radiative forcing over the Southern Hemisphere, while East Asia had the largest contribution to direct radiative forcing over the Northern Hemisphere. Knowing the source of sulfate and its contribution to energy balance is important for understanding changes in regional air quality and climate.

Summary

Researchers quantified the global source-receptor relationships of sulfate and its direct and indirect radiative forcing (DRF and IRF). They implemented a sulfur source-tagging technique into the Community Atmosphere Model (version 5) and performed simulations with time-varying sulfur release and meteorological conditions for the time period of 2010−2014. They found that, in regions with high sulfur release, near-surface sulfate concentrations mostly came from local sources. For regions with relatively low gaseous release, the model attributed the near-surface sulfate primarily to nonlocal sources via long-range transport. Europe contributed 16-20 percent of sulfate concentrations over North Africa, Russia, and Central Asia in all seasons. Sources from the Middle East accounted for 15-24 percent of sulfate over North Africa, Southern Africa, and Central Asia in winter and autumn, and 19 percent over South Asia in spring. East Asia accounted for about 50 percent of sulfate over Southeast Asia in winter and autumn, 15 percent over Russia in summer, and 11 percent over North America in spring. South Asia contributed to 11-24 percent of sulfate over Southeast Asia in winter and spring.

Contact
Hailong Wang
Pacific Northwest National Laboratory
Publications
Yang, Y., Wang, H., Smith, S., et al. "Global Source Attribution of Sulfate Concentration and Direct and Indirect Radiative Forcing." Atmospheric Chemistry and Physics 17, 8903-8922 (2017). [10.5194/acp-17-8903-2017].