| Black carbon concentration observation was made continuously at Shangdianzi regional GAW (Global Atmosphere Watch) station and Wenjiang site for one year, at Lin抋n regional GAW station for half year. Two other data sets were obtained from the long-term routine measurement at Mt. Waliguan Global GAW Observatory and the Lhasa experiment in 1998. The variation characteristics of black carbon at these five sites were analyzed combining with meteorological data of theirs. The background concentrations of black carbon were defined by using the statistical method and the lognormal curve fitting for these sites. The results showed that the background concentration of black carbon at Mt. Waliguan was lowest with a value of 73 ngm3, the one at Wenjiang site highest with a value of 2849 ngm3. The analysis of the Mt. Waliguan data set showed a long term increasing trend since mid nineties. The comparison of observation data with the existing model simulation result showed relative good agreement for Shangdianzi site but for other four sites. It may suggest the further investigation on the emission inventory/emission factor of black carbon for the more accurate modeling is necessary. Back trajectory analysis by using the cluster grouping method showed the obvious influence of long distance transportation on the variation of black carbon concentration at Mt. Waliguan, especially for the high episode periods in easterly flow.
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