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| Study on characteristic of aerosol extinction at Tianjin City in the spring |
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Abstract Based on the aerosol scattering and absorption coefficient, PM2.5 mass concentration, visibility and other observation data at Tianjin city, the characteristic of scattering and absorption coefficients and the relationship between aerosol extinction coefficient and PM2.5 mass concentration and visibility were analyzed. Two methods of calculating extinction coefficient were compared. The results indicated that mean aerosol scattering coefficient was 369.93Mm-1 and accounted for 86.7% of the extinction coefficient. Mean aerosol absorption coefficient was 36.32Mm-1 and accounted for 8.5%. The single scattering albedo was 0.91. Daily variation of aerosol scattering and absorption coefficients presented double-peak distributions corresponding to morning and evening rush hours. Aerosol scattering and absorption coefficients in haze days were highest and in dust days and rain days were middle and in sunny day were lowest. There was a good linear correlation between scattering or absorption coefficients and PM2.5 mass concentration and a typical negative exponential correlation with the visibility. The mean mass scattering efficiency was 2.95m2/g during observation period. The extinction coefficient retrieval from visibility with Koschmieder’s formula was consistent with the sum of observation aerosol scattering and absorption coefficients and gas scattering and absorption coefficients. The extinction coefficient retrieval value was higher than the observation when the relative humidity was higher than 80%.
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Received: 23 August 2011
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