| Atmospheric aerosol plays an important role in earth-atmospheric radiative budget andglobal climate change, and change the balance of the earth-atmospheric system through directand indirect radiative effect. Aerosol single scattering albedo (SSA) as well as sizedistributions are important optical properties, which determine the aerosol radiative effecttogether with aerosol optical depth and other properties. In recent years, Beijing witnessedthe surge of population and vehicles and rapid urbanization, leading to increasing amount ofemissions. Accurate estimate of aerosol optical properties in Beijing was not only to meet theneed to further understands the aerosol itself but also was a basis to calculate the radiativeforcing. Form October to Novonmber,2010, the measured aerosol optical depth and solardownwelling flux were combined to retrieve SSA in Beijing Institute of Technology; thefactors which could influence the diurnal variation of SSA were analyzed. Meanwhile, TSIaerodynamic particle sizer was used to measure the aerosol mass size distribution between0.5to20μm, and meteorological factor involved were also analyzed. In addition, aerosoldirect radiative forcing and its diurnal variation were modeled by the use of radiative transfermodel. The SSA in Xianghe were retrieved and analyzed. Some conclusions in thisdissertation are listed as below:The averaged SSA in BIT was0.893, and its standard deviation was0.053in1295samples. The SSA mean bias between the BIT and AERONET (IAP) were about0.030. Thediurnal SSA variation was obvious: the value was high at noon and low at about8:00and17:00. And the value was affected by the emission of black carbon from the vehicles duringrush hours. In addition, the SSA variation was influenced by the composition of the aerosolorganic and inorganic matter. SSA increased with the relative humidity. During hazy weather,the value of SSA increased rapidly.Under different weather conditions, the aerosol mass size distribution showed distinctdiscrepancies. These discrepancies were connected to with air mass (AM) movement. WhenBeijing was dominated by the air from north and northwest, aerosol concentration was lowand the peak showed at the coarse mode. While the wind and the air diffusive condition wasweak, accumulation of the pollutant in the city lead to peak values around0.52μm and5.50μm. In the condition of south and south-west wind prevailed, the peak showed at themine mode. The hygroscopic salt occupied a large proportion in Beijing, and the relative humidity and wind speed and orientations greatly affected the value of mass size distribution.During experimental period, the diurnal variation of aerosol direct radiative forcing(ARDF) were observed, which reached-127.212wm-2at noon and the value in the morningand evening were only half of this value. The ARDF at the top of atmosphere and in theatmosphere showed similar trend. The values at noon greatly contributed to the estimation ofthe whole day ARDF. The ARDF in Oct7th, Nov15th and Nov17th,2010showed distinctdifferences, and the aerosol optical depth with AM movement were important reasons. Thevalue of SSA also affected the Fs, which shows reverse trend with the variation of the SSA.The SSA in Xianghe from2005and2008were different from those calculated in Beijing.Compared to Beijing, the higher concentration ozone in Xianghe enhanced the conversion ofsulfate, and showed peak value afternoon. Meanwhile, SSA in Xianghe presented obviousseasonal variation with low value in Spring(about0.908) and high value in Summer(about0.926). The SSA also showed remarkable positive correlation with aerosol optical depthduring the whole year, while in winter the increased heating emission of black carbon sloweddown this trend. The aerosol properties are greatly affected by the AM movement, and SSAand size distribution showed notable characteristics with corresponding AM variation. |
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