01 Mar 2021

01 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

Evaluation of the contribution of new particle formation to cloud droplet in urban atmosphere

Sihui Jiang1, Fang Zhang1, Jingye Ren1, Lu Chen1, Xing Yan1, Jieyao Liu1, Yele Sun2, and Zhanqing Li3 Sihui Jiang et al.
  • 1College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
  • 2State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 3Earth System Science Interdisciplinary Center and Department of Atmospheric and Oceanic Science, University of Maryland, College Park, Maryland, USA

Abstract. New particle formation (NPF) is a large source of cloud condensation nuclei (CCN) and cloud droplet in the troposphere. In this study, we quantified the contribution of NPF to cloud droplet number concentration (CDNC, or Nd) at typical updraft velocities (V) in clouds using a field campaign data of aerosol number size distribution and chemical composition observed on May 25–June 18, 2017 in urban Beijing. We show that the NPF drives the variations of CCN and cloud droplet and increases Nd by 30–33 % at V = 0.3–3 m s−1 in urban atmosphere. A markedly reduction in Nd is observed due to water vapor competition with consideration of actual environmental updraft velocity, decreasing by 11.8 ± 5.0 % at V = 3 m s−1 and 19.0 ± 4.5 % at V = 0.3 m s−1 compared to that from a prescribed supersaturation. The effect of water vapor competition becomes smaller at larger V that can provide more sufficient water vapor. Essentially, water vapor competition led to the reduction in Nd by decreasing the environmental maximum supersaturation (Smax) for the activation of aerosol particles. It is shown that Smax was decreased by 14.5–11.7 % for V = 0.3–3 m s−1. Particularly, the largest suppression of cloud droplet formation due to the water vapor competition is presented at extremely high aerosol particle number concentrations. As a result, although a larger increase of CCN-size particles by NPF event is derived on clean NPF day when pre-existing background aerosol particles are very low, there is no large discrepancy in the enhancement of Nd by NPF between the clean and polluted NPF day. We finally show a considerable impact of the primary sources when evaluating the NPF contribution to cloud droplet based on a case study. Our study highlights the importance of fully consideration of both the environmental meteorological conditions and multiple sources (i.e. secondary and primary) to evaluate the NPF effect on clouds and the associated climate effects in polluted regions.

Sihui Jiang et al.

Status: open (until 26 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-23', Anonymous Referee #2, 25 Mar 2021 reply

Sihui Jiang et al.

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Evaluation of the contribution of new particle formation to cloud droplet in urban atmosphere Fang Zhang

Sihui Jiang et al.


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Short summary
New particle formation (NPF) can be a large source of CCN and affect weather and climate. Here we show that the NPF contributes largely to cloud droplet number concentration (Nd), but which is suppressed at high particle number concentrations in Beijing due to water vapor competition. We also reveal a considerable impact of the primary sources on the evaluation in urban atmosphere. Our study is with great significance to assess the NPF associated effects on climate in polluted regions.