Preprints
https://doi.org/10.5194/acp-2020-1238
https://doi.org/10.5194/acp-2020-1238

  18 Jan 2021

18 Jan 2021

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

Measurement report: The effect of aerosol chemical composition on light scattering due to the hygroscopic swelling effect

Rongmin Ren1, Zhanqing Li2, Peng Yan3, Yuying Wang4, Hao Wu5, Wei Wang1, Xiao'ai Jin1, Yanan Li3, Dongmei Zhang1, and Maureen Cribb2 Rongmin Ren et al.
  • 1State Key Laboratory of Remote Sensing Science, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
  • 2Earth System Science Interdisciplinary Center, Department of Atmospheric and Oceanic Science, University of Maryland, College Park, College Park, MD, USA
  • 3CMA Meteorological Observation Center, Centre for Atmosphere Watch and Services, Beijing 100081, China
  • 4Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 5School of Electrical Engineering, Chengdu University of Information Technology, Chengdu 610225, China

Abstract. Liquid water in aerosol particles has a significant effect on optical properties, especially on light scattering, whose dependence on chemical composition is investigated here using measurements made in southern Beijing in 2019. The effect is measured by the enhancement of aerosol hygroscopic factor, f(RH = 85 %, 525 nm), which is found to be positively and negatively impacted by the proportions of inorganic and organic matters respectively. Black carbon is also negatively correlated. The positive impact is more robust when the inorganic matter mass fraction was smaller than 40 % (correlation coefficient, R = 0.93) which becomes weaker as the inorganic matter mass fraction gets larger (R = 0.48). A similar pattern was also found in the negative impact for organic matter mass fraction. Nitrate played a more significant role in aerosol hygroscopicity than sulfate in Beijing. However, the deliquescence point of ambient aerosols was at about RH = 80 % when the ratio of the sulfate mass concentration to the nitrate mass concentration of the aerosol was high (mostly higher than ~4). Two schemes to parameterize f(RH) were developed in accounting for the deliquescent and non-deliquescent effects. Using only one f(RH) parameterization scheme to fit all f(RH) processes would incur large errors. A piecewise parameterization scheme is proposed, which can better describe deliquescence and reduces uncertainties in simulating aerosol hygroscopicity.

Rongmin Ren et al.

Status: open (until 15 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1238', Anonymous Referee #2, 08 Feb 2021 reply
  • RC2: 'Comment on acp-2020-1238', Anonymous Referee #1, 15 Feb 2021 reply

Rongmin Ren et al.

Rongmin Ren et al.

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Short summary
We analyzed the effect of the proportion of components making up the chemical composition of aerosols on f(RH) in southern Beijing in 2019. Nitrate played a more significant role in affecting f(RH) than sulfate. The ratio of the sulfate mass fraction to the nitrate mass fraction (mostly higher than ~4) was a sign of the deliquescence of aerosol. A piecewise parameterized scheme was proposed, which could better describe deliquescence and reduce uncertainties in simulating aerosol hygroscopicity.
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