%AGonzalez, Andres [Department of Soil, Water, and Climate University of Minnesota Saint Paul MN USA]%AMillet, Dylan [Department of Soil, Water, and Climate University of Minnesota Saint Paul MN USA]%AYu, Xueying [Department of Soil, Water, and Climate University of Minnesota Saint Paul MN USA]%AWells, Kelley [Department of Soil, Water, and Climate University of Minnesota Saint Paul MN USA]%AGriffis, Timothy [Department of Soil, Water, and Climate University of Minnesota Saint Paul MN USA]%ABaier, Bianca [Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado Boulder CO USA, Global Monitoring Laboratory National Oceanic and Atmospheric Administration Boulder CO USA]%ACampbell, Patrick [Center for Spatial Information Science and Systems George Mason University Fairfax VA USA, Cooperative Institute for Satellite Earth System Studies (CISESS) College Park MD USA, Air Resources Laboratory National Oceanic and Atmospheric Administration College Park MD USA]%AChoi, Yonghoon [NASA Langley Research Center Hampton VA USA]%ADiGangi, Joshua [NASA Langley Research Center Hampton VA USA]%AGvakharia, Alexander [Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor MI USA]%AHalliday, Hannah [NASA Langley Research Center Hampton VA USA]%AKort, Eric [Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor MI USA]%AMcKain, Kathryn [Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado Boulder CO USA, Global Monitoring Laboratory National Oceanic and Atmospheric Administration Boulder CO USA]%ANowak, John [NASA Langley Research Center Hampton VA USA]%APlant, Genevieve [Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor MI USA]%BJournal Name: Geophysical Research Letters; Journal Volume: 48; Journal Issue: 11; Related Information: CHORUS Timestamp: 2023-08-25 16:52:04 %D2021%IDOI PREFIX: 10.1029 %JJournal Name: Geophysical Research Letters; Journal Volume: 48; Journal Issue: 11; Related Information: CHORUS Timestamp: 2023-08-25 16:52:04 %K %MOSTI ID: 10375451 %PMedium: X %TFossil Versus Nonfossil CO Sources in the US: New Airborne Constraints From ACT‐America and GEM %XAbstract

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.

%0Journal Article