摘要
Aerosol Optical Thickness （AOT）, water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends and inter-annual variations are presented and discussed. Summer has the highest seasonal average AOT at 440 nm （τa440）, Angstrom exponent （α440-870） and water vapor content with the values 0.93, 1.34 and 3.0 cm, respectively. The second highest seasonal average τa440 appears in spring with the largest variation of α440-870 and minimum α440-870 0.99 due to the impact of coarse particles. The minimum seasonal average τa440 （0.44） and water vapor content （0.4 cm） appear in winter. The annual average τa440 , α440-870 and water vapor content for about 4-year observation period are 0.70, 1.19 and 1.4 cm, respectively. All monthly average Angstrom exponents are within 0.8-1.4. which indicates aerosol in Beijing is a very complex mixture of both fine- and coarse-mode particles （from anthropogenic influence and natural mineral dust）.
Aerosol Optical Thickness （AOT）, water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends and inter-annual variations are presented and discussed. Summer has the highest seasonal average AOT at 440 nm （τa440）, Angstrom exponent （α440-870） and water vapor content with the values 0.93, 1.34 and 3.0 cm, respectively. The second highest seasonal average τa440 appears in spring with the largest variation of α440-870 and minimum α440-870 0.99 due to the impact of coarse particles. The minimum seasonal average τa440 （0.44） and water vapor content （0.4 cm） appear in winter. The annual average τa440 , α440-870 and water vapor content for about 4-year observation period are 0.70, 1.19 and 1.4 cm, respectively. All monthly average Angstrom exponents are within 0.8-1.4. which indicates aerosol in Beijing is a very complex mixture of both fine- and coarse-mode particles （from anthropogenic influence and natural mineral dust）.
基金
This research is supported by a China-France PRA project, the National Science Foundation of China （40250120071）
the Chinese Academy of Sciences （2003-2-9）
