资源环境科技发展态势分析平台

We applied a global three-dimensional chemical transport model (GEOS-Chem) to examine the impacts of the East Asian monsoon on the interannual variations of mass concentrations and direct radiative forcing (DRF) of black carbon (BC) over eastern China (110-125 degrees E, 20-45 degrees N). With emissions fixed at the year 2010 levels, model simulations were driven by the Goddard Earth Observing System (GEOS-4) meteorological fields for 1986-2006 and the Modern Era Retrospective-analysis for Research and Applications (MERRA) meteorological fields for 1980-2010. During the period of 1986-2006, simulated June-July-August (JJA) and December-January-February (DJF) surface BC concentrations were higher in MERRA than in GEOS-4 by 0.30 gm 3 (44 %) and 0.77 gm 3 (54 %), respectively, because of the generally weaker precipitation in MERRA. We found that the strength of the East Asian summer monsoon (EASM; East Asian winter monsoon, EAWM) negatively correlated with simulated JJA (DJF) surface BC concentrations (r D 0 : 7 (0.7) in GEOS-4 and 0.4 (0.7) in MERRA), mainly by the changes in atmospheric circulation. Relative to the 5 strongest EASM years, simulated JJA surface BC concentrations in the 5 weakest monsoon years were higher over northern China (110-125 degrees E, 28-45 degrees N) by 0.040.09 mu gm 3 (3-11 %), but lower over southern China (110125 degrees E, 20-27 degrees N) by 0.03-0.04 mu gm 3 (10-11 %). Com-pared to the 5 strongest EAWM years, simulated DJF surface BC concentrations in the 5 weakest monsoon years were higher by 0.13-0.15 mu gm 3 (5-8 %) in northern China and by 0.04-0.10 mu gm 3 (3-12 %) in southern China. The resulting JJA (DJF) mean all-sky DRF of BC at the top of the atmosphere was 0.04Wm 2 (3 %; 0.03Wm 2, 2 %) higher in northern China but 0.06Wm 2 (14 %; 0.03Wm 2, 3 %) lower in southern China. In the weakest monsoon years, the weaker vertical convection at the elevated altitudes led to the lower BC concentrations above 1-2 km in southern China, and therefore the lower BC DRF in the region. The differences in vertical profiles of BC between the weakest and strongest EASM years (1998-1997) and EAWM years (1990-1996) reached up to 0.09 mu gm 3 (46 %) and 0.08 mu gm(3) (11 %) at 1-2 km in eastern China.