南京冬季云凝结核活化特征及闭合研究

2017年12月~2018年1月在南京地区对气溶胶的云凝结核（CCN）活化特征进行外场观测，并利用4种常用的闭合方法实现对CCN数浓度的预测.结果表明本次观测期间南京地区的气溶胶具有较高的CCN活性，吸湿性参数（κ）的平均值为0.36.对清洁到不同程度雾-霾天气溶胶污染的CCN活化特征进行对比分析，发现随着污染程度的加深，气溶胶的吸湿性逐渐减弱；在同一能见度（VIS）范围内，环境相对湿度（RH）更高的天气类型中气溶胶的吸湿性和活化能力也更高，这可能由于高RH条件能促进大气中非均相及液相反应生成更多的二次无机气溶胶.4种闭合方法的结果显示，利用临界粒径、截断粒径及粒径分辨的活化谱三种方法总体上均有较好的闭合结果.其中，对于低过饱和度（S）下的预测来说，利用截断粒径方法的闭合结果最为理想.

Characterization and prediction of cloud condensation nuclei activity in winter of Nanjing

The cloud condensation nuclei (CCN) activation properties of aerosols were measured from December 2017 to January 2018 in Nanjing, and four kinds of closure methods were used to predict the concentration of CCN. The results showed that the aerosols in Nanjing exhibited relatively high CCN activity during the observation period, with an average hygroscopicity parameter (κ) of 0.36. From a comparation of the CCN activation characteristics under clean and varying degrees of fog and haze conditions, it was found that the aerosol hygroscopicity gradually decreased as the pollution deteriorated. Within the same visibility (VIS) range, aerosol particles had higher hygroscopicity and activation capacity under higher relative humidity (RH). This may be because that high RH condition can promote heterogeneous and liquid phase reactions of gaseous species in the atmosphere to generate more secondary inorganic aerosols. The results of the four closure methods showed that the prediction of CCN number concentration by using critical diameters, cut-off diameters and size-resolved activation ratios generated better results in general. Among them, the method of cut-off diameters generated best results in predictions at low supersaturation (S).