Impacts of Meteorological Parameters and Emissions on Decadal and Interannual Variations of Black Carbon in China for 1980–2010

Abstract:

We quantified the impacts of variations in meteorological parameters and emissions on the decadal and interannual variations of surface black carbon (BC) concentrations in China for a 31-yr period (1980–2010) using a global chemical transport model (GEOS-Chem) driven by the MERRA meteorological fields. Relative to year 1980, simulated surface BC concentrations in year 2010 increased by 0.21 µg m^–3 (29%) averaged over China. The corresponding all-sky direct radiative forcing of BC at the top of the atmosphere increased by 0.35 W m^–2 (51%). Considering variations in both meteorological parameters and emissions for 1980–2010, simulated annual mean surface BC concentrations averaged over China were in the range of ~0.7–1.0 µg m^–3 and showed decadal trends of 0.31, –0.20, 0.16 µg m^–3 decade^–1, respectively, in the 1980s, 1990s, and 2000s. The associated interannual variations were –20 to 15%, 0.068 µg m^–3, and 7.7%, respectively, for the values of deviation from the mean, mean absolute deviation, and absolute percent departure from the mean. Model sensitivity simulations indicated that the decadal trends of surface BC concentrations were mainly driven by changes in emissions, while the interannual variations were dependent on variations of both emissions and meteorological parameters. We also found that the strength of the East Asian monsoon (either summer or winter monsoon) negatively correlated with surface BC concentrations in eastern China (20–45° N, 110–125° E) (r = -0.7), mainly by the changes in atmospheric circulation. Relative to the five strongest monsoon years, simulated surface BC concentrations over eastern China were higher by 2–10% in the five weakest monsoon years.