期刊
ATMOSPHERIC ENVIRONMENT
卷 45, 期 5, 页码 1162-1167出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.atmosenv.2010.10.054
关键词
Black carbon; Radiative forcing; Diesel emission control
资金
- California Air Resources Board (CARB) [08-323]
We examine the temporal and the spatial trends in the concentrations of black carbon (BC) - recorded by the IMPROVE monitoring network for the past 20 years - in California. Annual average BC concentrations in California have decreased by about 50% from 0.46 mu g m(-3) in 1989 to 0.24 mu gm(-3) in 2008 compared to the corresponding reductions in diesel BC emissions (also about 50%) from a peak of 0.013 Tg Yr(-1) in 1990 to 0.006 Tg Yr(-1) by 2008. We attribute the observed negative trends to the reduction in vehicular emissions due to stringent statewide regulations. Our conclusion that the reduction in diesel emissions is a primary cause of the observed BC reduction is also substantiated by a significant decrease in the ratio of BC to non-BC aerosols. The absorption efficiency of aerosols at visible wavelengths - determined from the observed scattering coefficient and the observed BC - also decreased by about 50% leading to a model-inferred negative direct radiative forcing (a cooling effect) of -1.4 W m(-2) (+/- 60%) over California. (C) 2010 Elsevier Ltd. All rights reserved.
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