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https://doi.org/10.5194/egusphere-2024-950
https://doi.org/10.5194/egusphere-2024-950
05 Apr 2024
 | 05 Apr 2024

Global Spatial Variation in the PM2.5 to AOD Relationship Strongly Influenced by Aerosol Composition

Haihui Zhu, Randall Martin, Aaron van Donkelaar, Melanie Hammer, Chi Li, Jun Meng, Christopher Oxford, Xuan Liu, Yanshun Li, Dandan Zhang, Inderjeet Singh, and Alexei Lyapustin

Abstract. Ambient fine particulate matter (PM2.5) is the leading global environmental determinant of mortality. However, large gaps exist in ground-based PM2.5 monitoring. Satellite remote sensing of aerosol optical depth (AOD) offers information to fill these gaps worldwide, when augmented with a modeled PM2.5 to AOD relationship (η). This study aims to understand the spatial pattern and driving factors of η from both observations and modeling. A global observational estimate of η for the year 2019 is inferred from 6,118 ground-based PM2.5 measurement sites and satellite retrieved AOD from the MAIAC algorithm. A global chemical transport model, GEOS-Chem, in its high performance configuration (GCHP), is used to interpret the observed spatial pattern of annual mean η. Measurements and the GCHP simulation consistently identify a global population-weighted mean η of 92 – 100 μg/m3, with regional values ranging from 60.3 μg/m3 for North America to more than 130 μg/m3 in Africa. The highest η is found in arid regions where aerosols are less hygroscopic due to mineral dust, followed by regions strongly influenced by surface aerosol sources. Relatively low η is found over regions distant from strong aerosol sources. The spatial variation of η is strongly influenced by aerosol composition driven by its effects on aerosol hygroscopicity. Sensitivity tests with globally uniform parameters reveal that aerosol composition leads to the strongest η spatial variability, with a population-weighted normalized mean difference of 12.3 μg/m3, higher than that from aerosol vertical profile (8.4 μg/m3), reflecting the determinant composition effects on aerosol hygroscopicity and aerosol optical properties.

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Haihui Zhu, Randall Martin, Aaron van Donkelaar, Melanie Hammer, Chi Li, Jun Meng, Christopher Oxford, Xuan Liu, Yanshun Li, Dandan Zhang, Inderjeet Singh, and Alexei Lyapustin

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-950', Anonymous Referee #1, 02 May 2024
  • RC2: 'Comment on egusphere-2024-950', Anonymous Referee #2, 24 May 2024
Haihui Zhu, Randall Martin, Aaron van Donkelaar, Melanie Hammer, Chi Li, Jun Meng, Christopher Oxford, Xuan Liu, Yanshun Li, Dandan Zhang, Inderjeet Singh, and Alexei Lyapustin
Haihui Zhu, Randall Martin, Aaron van Donkelaar, Melanie Hammer, Chi Li, Jun Meng, Christopher Oxford, Xuan Liu, Yanshun Li, Dandan Zhang, Inderjeet Singh, and Alexei Lyapustin

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Short summary
Ambient fine particulate matter (PM2.5) contributes to 4 million deaths every year globally. Satellite remote sensing of aerosol optical depth (AOD) coupled with a simulated PM2.5 to AOD relationship (η) can provide global PM2.5 estimation. This study aims to understand the spatial pattern and driving factors of η to guide future measurement and model efforts. We quantified η globally and regionally and found its spatial variation is strongly influenced by the aerosol composition.