Preprints
https://doi.org/10.5194/egusphere-2024-479
https://doi.org/10.5194/egusphere-2024-479
12 Mar 2024
 | 12 Mar 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Technical note: Influence of different averaging metrics and temporal resolutions on aerosol pH calculated by thermodynamic modeling

Haoqi Wang, Xiao Tian, Wanting Zhao, Jiacheng Li, Haoyu Yu, Yinchang Feng, and Shaojie Song

Abstract. Aerosol pH is commonly used to characterize the acidity of aqueous aerosols and is of significant scientific interest due to its close relationship with atmospheric processes. Estimation of ambient aerosol pH usually relies on the thermodynamic modeling approach. In the existing chemical transport model and field observation studies, the temporal resolution of the input chemical and meteorological data into thermodynamic models varied substantially ranging from less than an hour to a year because of the inconsistency in the resolution of the original data and the aggregation of time-series data in some studies. Furthermore, the average value of aerosol pH has been represented by diverse metrics of central tendency in existing studies. This study attempts to evaluate the potential discrepancies in the calculated average aerosol pH arising from differences in both averaging metrics and temporal resolutions based on the ISORROPIA-II thermodynamic model and the example datasets prepared by the GEOS-Chem chemical transport model simulation. Overall, we find that the variation in the temporal resolutions of input data may lead to a change of up to more than two units in the average pH, and that the averaging metrics calculated based on the pH value of individual samples may be about two units higher than the averaging metrics calculated based on the activity of hydrogen ions. Accordingly, we recommend that the chosen averaging metrics and temporal resolutions should be stated clearly in future studies to ensure comparability of the average aerosol pH between models and/or observations.

Haoqi Wang, Xiao Tian, Wanting Zhao, Jiacheng Li, Haoyu Yu, Yinchang Feng, and Shaojie Song

Status: open (until 23 Apr 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-479', Anonymous Referee #2, 18 Mar 2024 reply
  • RC2: 'Comment on egusphere-2024-479', Anonymous Referee #1, 27 Mar 2024 reply
Haoqi Wang, Xiao Tian, Wanting Zhao, Jiacheng Li, Haoyu Yu, Yinchang Feng, and Shaojie Song
Haoqi Wang, Xiao Tian, Wanting Zhao, Jiacheng Li, Haoyu Yu, Yinchang Feng, and Shaojie Song

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Short summary
pH is a key property of ambient aerosols affecting many atmospheric processes. As aerosol pH is a non-conservative parameter, diverse averaging metrics and temporal resolutions may influence its calculation results from thermodynamic models. This technical note seeks to quantitatively evaluate the average pH using varied metrics and resolutions. The ultimate goal is to establish standardized reporting practices in future research endeavors.