Variation of CCN activity during new particle formation events in the North China Plain

Abstract

Abstract. The aim of this investigation was to obtain a better understanding of the variability of the cloud condensation nuclei (CCN) activity during new particle formation (NPF) events in an anthropogenically polluted atmosphere of the North China Plain (NCP). We investigated the size-resolved activation ratio as well as particle number size distribution, hygroscopicity, and volatility during a 4-week intensive field experiment in summertime at a regional atmospheric observatory in Xianghe. Interestingly, based on a case study, two types of NPF events were found, in which the newly formed particles exhibited either a higher or a lower hygroscopicity. Therefore, the CCN activity of newly formed particles in different NPF events was largely different, indicating that a simple parameterization of particle CCN activity during NPF events over the NCP might lead to poor estimates of CCN number concentration (NCCN). For a more accurate estimation of the potential NCCN during NPF events, the variation of CCN activity has to be taken into account. Considering that a fixed activation ratio curve or critical diameter are usually used to calculate NCCN, the influence of the variation of particle CCN activity on the calculation of NCCN during NPF events was evaluated based on the two parameterizations. It was found that NCCN might be underestimated by up to 30 % if a single activation ratio curve (representative of the region and season) were to be used in the calculation; and might be underestimated by up to 50 % if a fixed critical diameter (representative of the region and season) were used. Therefore, we suggest not using a fixed critical diameter in the prediction of NCCN in NPF. If real-time CCN activity data are not available, using a proper fixed activation ratio curve can be an alternative but compromised choice.

Sizing of Ambient Particles From a Single‐Particle Soot Photometer Measurement to Retrieve Mixing State of Black Carbon at a Regional Site of the North China Plain

“…The Xianghe site is at a polluted suburban area of NCP and locates between capital Beijing (~60 km) and megacity Tianjin (~100 km). More derails on this site were descripted by Ma et al (2016), Kecorius et al (2015), Raatikainen et al (2017), and Zhang et al (2016). The BC-containing particles over the regional site are influenced by various sources (e.g., traffic and industry emissions and biomass burning).…”

Enhanced hydrophobicity and volatility of submicron aerosols under severe emission control conditions in Beijing

“…The mixing state of ambient aerosol particles is complex due to different sources, different aging processes, and so on. Different hygroscopic and volatile groups had been used around the Beijing region using H-TDMAs and V-TDMAs (Massling et al, 2009;Liu et al, 2011;S. L. Zhang et al, 2016).…”

“…For submicron particles, NV part particles at 300 • C were normally the major NH part particles because both their main components are soot particles (Massling et al, 2009;Wehner et al, 2009). S. L. compared the relationship between the number fraction of measured nonvolatile particles (NF NV ) and nearly hydrophobic (NF NH ) particles and found those two groups are very likely to be dominated by the same component.…”

A New Method for Distinguishing Unactivated Particles in Cloud Condensation Nuclei Measurements: Implications for Aerosol Indirect Effect Evaluation

“…In the 2000s, the continuous-flow streamwise thermal-gradient CCN counter from Droplet Measurement Technologies (DMT-CCNC) became commercially available with enhanced robustness and reliability (Roberts & Nenes, 2005). Based on DMT-CCNC measurements, scientists have conducted extensive field observations and laboratory experiments for CCN around the world and obtained many valuable results (e.g., Ma et al, 2016;Mochida et al, 2011;Quinn et al, 2017;Yum et al, 2007;Zhang et al, 2012 However, unactivated particles, which are not authentic CCN at the specific SS, are included in the measurements of CCN at low SS conditions (Roberts & Nenes, 2005). The overestimation of N CCN caused by unactivated particles results in underestimation of droplet radii, including the effective radius and volume weighted mean radius when liquid water content is constant (Albrecht, 1989;Twomey, 1974Twomey, , 1977.…”

“…In the 2000s, the continuous-flow streamwise thermal-gradient CCN counter from Droplet Measurement Technologies (DMT-CCNC) became commercially available with enhanced robustness and reliability (Roberts & Nenes, 2005). Based on DMT-CCNC measurements, scientists have conducted extensive field observations and laboratory experiments for CCN around the world and obtained many valuable results (e.g., Ma et al, 2016;Mochida et al, 2011;Quinn et al, 2017;Yum et al, 2007;Zhang et al, 2012).…”