关键词: 气溶胶, CCN, 飞机观测, 雾霾, 谱分布

Abstract:

Aircraft measurements of atmospheric aerosol and cloud condensation nuclei (CCN) over the central and southern Hebei were carried out in autumn of 2009. The spatial distribution, source of aerosol and its relationship with CCN under foggy/hazy weather condition were analyzed. The results show that there was a significant difference in the vertical distribution of aerosol number concentration near the boundary layer. The aerosol number concentration decreased with height above boundary layer, it was about in 101-102 order of magnitude. There was a peak value of aerosol number concentration near the boundary layer and near-surface. The aerosol number concentration was in 103 order of magnitude  near surface. The range of aerosol mean diameters was between 0.16 and 0.18 μm. The aerosol size distribution showed an unimodal mode on 600 m, between 1 000 and 2 000 m, while from 3 000 to 4 000 m, 6 000 to 6 900 m it showed a bimodal (multimodal) mode. Due to the different sources of aerosol, the conversion ratio of aerosol to CCN was less than 20% below 3 000 m, and it reached 50% above the level at 0.3% super-saturation. The air mass back trajectories showed that the aerosols at higher levels above 6 000 m were affected by the long distance transport from the northwest, the dust might be transformed to CCN. The aerosols at lower levels were affected by local pollution, therefore the particle size was smaller and the conversion ratio of aerosol to CCN was lower than that at higher level. The CCN concentration increased with super-saturation. The aerosol and CCN concentrations at different height were fitted with polynomial function. The relationship between aerosol and CCN concentration was established.

Key words: aerosol, CCN, airplane observation, fog/hazy, size distribution