Preprints
https://doi.org/10.5194/acp-2021-922
https://doi.org/10.5194/acp-2021-922
 
21 Jan 2022
21 Jan 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Ice nucleating particles from multiple aerosol sources in the urban environment under mixed-phase cloud conditions

Cuiqi Zhang1, Zhijun Wu1,2, Jingchuan Chen1, Jie Chen1,a, Lizi Tang1, Wenfei Zhu1, Xiangyu Pei4, Shiyi Chen1, Ping Tian5, Song Guo1, Limin Zeng1, Min Hu1, and Zamin A. Kanji3 Cuiqi Zhang et al.
  • 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
  • 2Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 3Institute for Atmospheric and Climate Science, ETHZ, Zurich, 8092, Switzerland
  • 4College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
  • 5Beijing Weather Modification Center, Beijing, 100089, China
  • anow at: Institute for Atmospheric and Climate Science, ETHZ, Zurich, 8092, Switzerland

Abstract. Ice crystals occurring in mixed-phase clouds play a vital role in global precipitation and energy balance because of the unstable equilibrium between co-existent liquid droplets and ice crystals, which affects cloud lifetime and radiative properties, as well as precipitation formation. Satellite observations proved that immersion freezing, i.e., ice formation on particles immersed within aqueous droplets, is the dominant ice nucleation (IN) pathway in mixed-phase clouds. However, the impact of anthropogenic emission on atmospheric IN in the urban environment remains ambiguous. In this study, we present in situ observations of ambient ice nucleating particle number concentration (NINP) measured at mixed-phase cloud conditions (−30 °C, relative humidity with respect to liquid water RHw = 104 %) and the physicochemical properties of ambient aerosol, including chemical composition and size distribution, at an urban site in Beijing during the traditional Chinese Spring Festival. The impact of multiple aerosol sources such as firework emissions, local traffic emissions, mineral dust and urban secondary aerosols on NINP is investigated. The results show that NINP during the dust event reaches up to 160 # L−1, with an activation fraction (AF) of 0.0036 % ± 0.0011 %. During the rest of the observation, NINP is on the order of 10−1 to 10 # L−1, with an average AF between 0.0001 to 0.0002 %. No obvious dependence of NINP on the number concentration of particles larger than 500 nm (N500) or black carbon (BC) mass concentration (mBC) is found throughout the field observation. The results indicate that mineral dust dominates NINP, although the observation took place at an urban site with high background aerosol concentration. Meanwhile, the presence of atmospheric BC from firework and traffic emissions, along with urban aerosols formed via secondary transformation during heavily polluted periods do not influence the observed INP concentration. Our study corroborates previous laboratory and field findings that anthropogenic BC emission has a negligible effect on NINP, and that NINP is unaffected by heavy pollution in the urban environment under mixed-phase cloud conditions.

Cuiqi Zhang et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-922', Anonymous Referee #1, 12 Feb 2022
  • RC2: 'Referee Comment on acp-2021-922', Anonymous Referee #2, 03 Mar 2022
  • AC1: 'Response to referee comments', Cuiqi Zhang, 25 Apr 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-922', Anonymous Referee #1, 12 Feb 2022
  • RC2: 'Referee Comment on acp-2021-922', Anonymous Referee #2, 03 Mar 2022
  • AC1: 'Response to referee comments', Cuiqi Zhang, 25 Apr 2022

Cuiqi Zhang et al.

Cuiqi Zhang et al.

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Short summary
The immersion ice nucleation effectiveness of aerosols from multiple sources in the urban environment remains elusive. In this study, we demonstrate that mineral dust still dominates the immersion ice nucleating particle (INP) population despite the high background urban particle number concentration. Pollutant aerosols, including inorganic salts formed through secondary transformation (SIA) and black carbon (BC), might not act as effective INP under mixed-phase cloud conditions.
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