25 Nov 2022
25 Nov 2022
Status: this preprint is currently under review for the journal ACP.

Source attribution of near-surface ozone trends in the United States during 1995–2019

Pengwei Li1, Yang Yang1, Hailong Wang2, Su Li1, Ke Li1, Pinya Wang1, Baojie Li1, and Hong Liao1 Pengwei Li et al.
  • 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring andPollution Control, Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China
  • 2Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington, USA

Abstract. Emissions of ozone (O3) precursors in the United States have decreased in recent decades, and near-surface O3 concentrations showed a significant decrease in summer but an increase in winter. In this study, an O3 source tagging technique is utilized in a chemistry-climate model to investigate the source contributions to O3 concentrations in the U.S. from various emitting sectors and regions of nitrogen oxides (NOx) and reactive carbon species during 1995–2019. We show that domestic emission reductions from energy and surface transportation are primarily responsible for the decrease in summertime O3 during 1995–2019. However, in winter the emission control also weakens the NOx titration process, resulting in considerable increases in O3 levels from natural sources. Additionally, increases in aviation and shipping activities and transpacific transport of O3 from Asia largely contribute to the winter O3 increase. Changes in large-scale circulation also explain 15 % of the O3 increasing trend.

Pengwei Li et al.

Status: open (until 06 Jan 2023)

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Pengwei Li et al.


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Short summary
We use a novel technique that can attribute O3 to precursors to investigate O3 changes in the United States during 1995–2019. We found that the U.S. domestic energy and surface transportation emission reductions are primarily responsible for the O3 decrease in summer. In winter, factors such as nitrogen oxides emissions reduction in the context of its inhibition of ozone production, increased aviation and shipping activities, and large-scale circulation changes contribute to the O3 increases.