Fossil Versus Nonfossil CO Sources in the US: New Airborne Constraints From ACT-America and GEM

Andres Gonzalez, Dylan B. Millet, Xueying Yu, Kelley C. Wells, Timothy J. Griffis, Bianca C. Baier, Patrick C. Campbell, Yonghoon Choi, Joshua P. DiGangi, Alexander Gvakharia, Hannah S. Halliday, Eric A. Kort, Kathryn McKain, John B. Nowak, Genevieve Plant

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Carbon monoxide (CO) is an ozone precursor, oxidant sink, and widely used pollution tracer. The importance of anthropogenic versus other CO sources in the US is uncertain. Here, we interpret extensive airborne measurements with an atmospheric model to constrain US fossil and nonfossil CO sources. Measurements reveal a low bias in the simulated CO background and a 30% overestimate of US fossil CO emissions in the 2016 National Emissions Inventory. After optimization we apply the model for source partitioning. During summer, regional fossil sources account for just 9%–16% of the sampled boundary layer CO, and 32%–38% of the North American enhancement—complicating use of CO as a fossil fuel tracer. The remainder predominantly reflects biogenic hydrocarbon oxidation plus fires. Fossil sources account for less domain-wide spatial variability at this time than nonfossil and background contributions. The regional fossil contribution rises in other seasons, and drives ambient variability downwind of urban areas.

Original languageEnglish (US)
Article numbere2021GL093361
JournalGeophysical Research Letters
Issue number11
StatePublished - Jun 5 2021

Bibliographical note

Funding Information:
This work was supported by NASA (Grant #NNX17AK18G) and the Minnesota Supercomputing Institute. This work was also supported in part by NSF Grant #1650682 (E. A. Kort, A. Gonzalez, and G. Plant) and by NASA Grants #NNX15AJ06G (B. C. Baier), #NNX15AJ23G (ATom campaign), and #80NSSC18K1393 (X. Yu). The authors thank K. Davis, Z. Barkley, and the entire ACT‐America team for their contributions.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.


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