The atmospheric aerosol distribution,source and relationship with cloud condensation nuclei(CCN) observed during the Beijing Cloud Experiment(BCE) are analyzed.The results show that the high number concentrations of aerosol mainly distributed below 4500 m,and the magnitude could reach to 103 cm 3.Above 4500 m,the aerosol number concentrations decreased to 101 cm 3 as the altitude increases,and the aerosol mean diameters were between 0.16 and 0.19 μm.Below 4500 m,the number size distributions of aerosol showed a bimodal(multimodal) mode,and an unimodal mode above it.Due to the different sources of aerosol,the conversion ratios of aerosol to CCN were less than 20% below 4500 m,and reached 50% above the level at 0.3% supersaturation.The back trajectories showed that aerosols at higher levels above 4500 m were strongly affected by large-size particles and those below 4500 m were strongly affected by local or regional pollution.Based on observations,a relationship between the CCN number concentration and aerosol number concentration is established.
