Preprints
https://doi.org/10.5194/acp-2022-787
https://doi.org/10.5194/acp-2022-787
 
29 Nov 2022
29 Nov 2022
Status: this preprint is currently under review for the journal ACP.

Quantifying particle-to-particle heterogeneity in aerosol hygroscopicity

Liang Yuan1,2 and Chunsheng Zhao2 Liang Yuan and Chunsheng Zhao
  • 1Chengdu Plain Urban Meteorology and Environment Scientific Observation and Research Station of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China
  • 2Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, 100871, China

Abstract. The particle-to-particle heterogeneity in aerosol hygroscopicity is crucial for understanding aerosol climatic and environmental effects. The hygroscopic parameter κ, widely applied to describe aerosol hygroscopicity for aerosol populations both in models and observations, is a probability distribution highly related to aerosol heterogeneity due to the complex sources and aging processes. However, the heterogeneity in aerosol hygroscopicity is not represented in observations and model simulations, leading to challenges in accurately estimating aerosol climatic and environmental effects. Here, we propose an algorithm for quantifying particle-to-particle heterogeneity in aerosol hygroscopicity, based on information-theoretic entropy measures, by using the data that comes only from the in-situ measurement of the hygroscopicity tandem differential mobility analyzer (H-TDMA). Aerosol populations in this algorithm are assumed to be simple binary systems consisting of the less hygroscopic and more hygroscopic components, which are commonly used in H-TDMA measurement. Three indices, including the aver age per-particle species diversity Dα, the bulk population species diversity Dγ, and their affine ratio χ, are calculated from the probability distribution of κ to describe aerosol heterogeneity. This algorithm can efficiently characterize the evolution of aerosol heterogeneity with time in the real atmosphere. Our results show that the heterogeneity varies much with aerosol particle size and large discrepancies exist in the width and peak value of particle number size distribution (PNSD) with varied heterogeneity after hygroscopic growth, especially for conditions with high relative humidity. This reveals a vital role of the heterogeneity in ambient PNSD and significant uncertainties in calculating the climate-relevant properties if the populationaveraged hygroscopicity is applied by neglecting its heterogeneity. This work points the way toward a better understanding of the role of hygroscopicity in evaluating aerosol climatic and environmental impacts.

Liang Yuan and Chunsheng Zhao

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-787', Anonymous Referee #1, 09 Jan 2023
  • RC2: 'Comment on acp-2022-787', Anonymous Referee #2, 29 Jan 2023

Liang Yuan and Chunsheng Zhao

Liang Yuan and Chunsheng Zhao

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Short summary
Chemical compositions variy between and within particles due to the complex sources and aging processes, causing particle-to-particle heterogeneity in aerosol hygroscopicity, which is of great importance to aerosol climatic and environmental effects. This study proposes an algorithm to quantify the heterogeneity from in-situ measurements, providing a framework for merging observation into numerical model to investigate how the heterogeneity influences aerosol impacts on climate and environment.
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