Aerosol hygroscopicity and cloud condensation nuclei activity during the AC 3 Exp campaign: implications for cloud condensation nuclei parameterization

作者：Fang Zhang, Y. Li, Zhanqing Li, Li Sun, Ruiyu Li, Chuanfeng Zhao, Pucai Wang, Yele Sun, Xinyuan Liu, Jingfa Li, P. Li, Gang Ren, Tianyi Fan · 发表于：Atmospheric chemistry and physics · 年份：2014 · DOI：10.5194/acp-14-13423-2014 · 被引用次数：93 · 研究领域：Atmospheric chemistry and aerosols、Atmospheric aerosols and clouds、Air Quality and Health Impacts

Abstract. Aerosol hygroscopicity and cloud condensation nuclei (CCN) activity under background conditions and during pollution events are investigated during the Aerosol-CCN-Cloud Closure Experiment (AC3Exp) campaign conducted at Xianghe, China in summer 2013. A gradual increase in size-resolved activation ratio (AR) with particle diameter (Dp) suggests that aerosol particles have different hygroscopicities. During pollution events, the activation diameter (Da) measured at low supersaturation (SS) was significantly increased compared to background conditions. An increase was not observed when SS was > 0.4%. The hygroscopicity parameter (κ) was ~ 0.31–0.38 for particles in accumulation mode under background conditions. This range in magnitude of κ was ~ 20%, higher than κ derived under polluted conditions. For particles in nucleation or Aitken mode, κ ranged from 0.20–0.34 for background and polluted cases. Larger particles were on average more hygroscopic than smaller particles. The situation was more complex for heavy pollution particles because of the diversity in particle composition and mixing state. A non-parallel observation CCN closure test showed that uncertainties in CCN number concentration estimates ranged from 30–40%, which are associated with changes in particle composition as well as measurement uncertainties associated with bulk and size-resolved CCN methods. A case study showed that bulk CCN activation ratios increased as total condensation nuclei (CN) numb...