Abstract. The global source-receptor relationships of sulfate concentration, direct and indirect radiative forcing (DRF and IRF) from sixteen regions/sectors for years 2010–2014 are examined in this study through utilizing a sulfur source-tagging capability implemented in the Community Earth System Model (CESM) with winds nudged to reanalysis data. Sulfate concentrations are mostly contributed by local emissions in regions with high emissions, while over regions with relatively low SO2 emissions, the near-surface sulfate concentrations are primarily attributed to non-local sources from long-range transport. The export of SO2 and sulfate from Europe contributes 16–20 % of near-surface sulfate concentrations over North Africa, Russia/Belarus/Ukraine (RBU) region and Central Asia. Sources from the Middle East account for 15–24 % of sulfate over North Africa, Southern Africa and Central Asia in winter and autumn, and 19 % over South Asia in spring. Sources in RBU account for 21–42 % of sulfate concentrations over Central Asia. East Asia accounts for about 50 % of sulfate over Southeast Asia in winter and autumn, 15 % over RBU in summer, and 11 % over North America in spring. South Asia contributes to 11–24 % of sulfate over Southeast Asia in winter and spring. Regional source efficiencies of sulfate concentrations are higher over regions with dry atmospheric conditions and less export, suggesting that lifetime of aerosols, together with regional export, is important in determining regional air quality. The simulated global total sulfate DRF is −0.42 W m−2, with 0.31 W m−2 contributed by anthropogenic sulfate and −0.11 W m−2 contributed by natural sulfate, relative to a state with no sulfur emissions. In the Southern Hemisphere tropics, dimethyl sulfide (DMS) contributes 17–84 % to the total DRF. East Asia has the largest contribution of 20–30 % over the Northern Hemisphere mid- and high-latitudes. A 20 % perturbation of sulfate and its precursor emissions gives a sulfate incremental IRF of −0.44 W m−2. DMS has the largest contribution, explaining −0.23 W m−2 of the global sulfate incremental IRF. Incremental IRF over regions in the Southern Hemisphere with low background aerosols is more sensitive to emission perturbation than those over the polluted Northern Hemisphere.
Global source attribution of sulfate concentration, direct and indirect radiative forcing
