Urbanization, Energy, and Air Pollution in China The Challenges Ahead: Proceedings of a Symposium (2004) / Chapter Skim
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Radiative Forcing by Anthropogenic Aerosols: Sources and Impacts--MICHAEL H. BERGIN
Radiative Forcing by Anthropogenic Aerosols: Sources and Impacts--MICHAEL H. BERGIN
Pages 155-168
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From page 155... ...
The cooling trend has been evident since the mid-1970s, which coincides with the start of economic reforms and intense industrialization in the area and has been accompanied by significant decreases in visual range, attributed to increases in anthropogenic aerosol loading.
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From page 156... ...
The indirect effects are attributable to changes in the optical properties of clouds associated with the presence of anthropogenic aerosol particles. Although much of China has a characteristic haziness, not much is known about the sources of aerosols and their impact on radiation balance, climate, and plant growth.
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From page 157... ...
NAAQS values. The chemical composition of fine particulate matter was dominated by carbonaceous aerosol and sulfate.
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From page 158... ...
Thus, the rural region of the Yangtze delta, one of the most important agricultural areas in China, appears to have relatively poor air quality as a result of both local emissions and the transport of polluted air from industrialized regions. Overall, many of the studies suggest extremely high aerosol loadings in urban and some rural areas of China, with primary anthropogenic contributions to fine particulate mass of sulfate and carbonaceous compounds.
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From page 159... ...
Although the model estimates probably reflect the impact of SO2 emissions on aerosol loadings, they only very roughly reflect the influence of particulate organic carbon, because neither elemental carbon nor organic carbon emissions are taken into account directly. Nor does the model take into account the contribution of dust to annual aerosol loading, which, as discussed above, can account for a significant fraction of the fine particulate mass, particularly during the spring season in much of northern China.
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From page 160... ...
Given these extremely high aerosol loadings, aerosols probably also have an FIGURE 2 Annual average aerosol optical depth at 550 nm (a) estimated by the model of Chameides et al., 1999.
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From page 161... ...
, the indirect aerosol radiative forcing in the Yangtze delta region is roughly 18 W/m2. Thus, the combined aerosol radiative forcing over much of China impacted by aerosols, taken as the sum of the direct and indirect effects, may be from 30 to 40 W/m2.
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From page 162... ...
measured in the Yangtze delta region during November 1999. NPAR and aerosol optical depth are both normalized to account for the change in 425 375 )
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From page 163... ...
The slope of the line, commonly called the direct aerosol radiative forcing efficiency, indicates a decrease in NPAR of ~74 W/m2 for each unit of aerosol optical depth. Based on Figure 4 and measurements of aerosol properties, Xu et al.
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From page 164... ...
The gray area shown in the middle is the most likely expected crop yield, based on limited knowledge of rice crop response as a function of diffuse fraction and aerosol optical depth values in China. The estimates suggest that the decrease in crop yield ranges from a few percent to nearly 10 percent.
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From page 165... ...
This decrease is associated with the scattering and absorption of light by anthropogenic aerosols. Recent model estimates suggest that the aerosol loadings over China may be influencing weather not only in China, but also elsewhere around the globe.
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From page 166... ...
2002. Correla tion between model-calculated anthropogenic aerosols and satellite-derived cloud optical depths: indication of indirect effect?
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From page 167... ...
2003. Direct aerosol radiative forcing in the Yangtze delta region of China: observation and model estimation.
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