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| An observation study of the scattering properties of aerosols over Shijiazhuang City in spring |
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Abstract The data measured by a three-wavelength integrating nephelometer, a PCASP-X2 and a visibility meter over Shijiazhuang, Hebei Province, China, from May 7~23, 2010, were used to investigate the scattering properties of aerosol particles and the relationship with particle size spectra, visibility and meteorological conditions. The results show that the scattering coefficients were (257±293), (199±237), and (143±173) Mm-1, respectively, for the three wavelengths, 450, 550 and 700 nm, and that the values varied significantly from day to day, while the microphysical property of aerosol is stable. It was also found that the daily variation of the aerosol scattering coefficient was a tri-peak shape, with the coefficient reaching peak values at about 8, 13 and 0 o’clock, respectively, and higher values were measured during nighttime. There was also a significant difference in the mean scattering coefficient under different weather conditions, with the mean value (524.9Mm-1) of overcast days was 4.7 times higher than that of fine days (112.3Mm-1). The ratios of backscattering coefficient to the total scattering coefficient of three wavelengths were all larger than 0.15, indicating that a significant fraction of the particular matter in Shijiazhuang was attributed to fine mode particles. There existed a positive correlation between the scattering coefficient and the volume concentration of aerosol, but sometimes when the volume concentration
was large, the scattering coefficient was small, maybe because of the local emission source or meteorological condition. There was a negative correlation between the scattering coefficient and visibility. Our results also find that the scattering coefficient would exhibit two different trends when the relative humidity increases, and the local wind direction and speed could also influence the scattering properties of aerosol.
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Received: 31 July 2011
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