The important roles of surface tension and growth rate in the contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration: evidence from field measurements in southern China
- 1Institute for Environmental and Climate Research, Jinan University, Guangzhou, Guangdong 511443, China
- 2Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, Guangdong 511443, China
- 3School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, and Institute of Earth Climate and Environment System, Sun Yat-sen University, Zhuhai, Guangdong 519082, China
- 4Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction, CMA, Guangzhou 510640, China
- 5Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, Guangdong 519082, China
- 6Laboratory of straits meteorology, Xiamen, Guangdong 361012, China
- 7Guangdong Provincial Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou, Guangdong 510275, China
Abstract. The contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration varies largely under different environments, depending on several key factors such as formation rate (J), growth rate (GR), distribution of preexisting particles and properties of new particles during NPF events. This study investigated the contribution of NPF to the NCCN and its controlling factors based on measurements conducted at the Heshan supersite, in the Pearl River Delta (PRD) region of China during fall-time 2019. The size-resolved cloud condensation nuclei activity and size-resolved particle hygroscopicity were measured by a cloud condensation nuclei counter (CCNc) and a hygroscopic tandem differential mobility analyzer (HTDMA), respectively, along with a scanning mobility particle sizer (SMPS) and a diethylene glycol scanning mobility particle sizer (DEG-SMPS) for particle number size distribution (PNSD). A typical NPF event on 29th October was chosen to investigate the contribution of the NPF to NCCN under several supersaturation ratios. Two particle properties (hygroscopicity and surface tension) affect CCN activation with the latter being more important in terms of the CCN concentration (NCCN). A lower value of surface tension (i.e., 0.06 N m−1) than pure water assumption (0.073 N m−1) could increase the NCCN at SS = 1.0 % by about 20 % during non-event period and by about 40 % during the event. In addition, an earlier peak time corresponding to a lower critical diameter (D50) was also observed. The results show that high formation rate, growth rate, and low background particle concentration lead to high number concentrations of newly-formed particles. The high growth rate was found to have the most profound impact on the NCCN which can be attributed to the facts that a higher growth rate can grow particles to the CCN size in a shorter time before they are scavenged by pre-existing particles. Two other NPF events (an event on 18th October in this campaign and an event on 12th December, 2014 in Panyu) were chosen to perform sensitivity tests under different scenarios (growth rate, formation rate, and background particle concertation). The calculated NCCN at SS = 1.0 % on 12th December, 2014 was significantly lower than that from the other two events. The event on 12th December was re-simulated using high growth rate taken from the event on 18th October which resulted in similar CCN concentrations between the two events (12th December and 18th October), implying that the growth rate is the most controlling factor for CCN activation. Our results highlight the importance of growth rate and surface tension when evaluating the contribution of NPF to the NCCN.
Mingfu Cai et al.
Mingfu Cai et al.
Mingfu Cai et al.
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