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Published July 8, 2025 | Version Published
Journal Article Open

Ozone Production Efficiencies in the Three Largest United States Cities from Airborne Measurements

Creators

  • 1. ROR icon Cooperative Institute for Research in Environmental Sciences
  • 2. ROR icon University of Colorado Boulder
  • 3. ROR icon National Oceanic and Atmospheric Administration
  • 4. ROR icon California Institute of Technology
  • 5. ROR icon Forschungszentrum Jülich
  • 6. ROR icon University of Cologne
  • 7. ROR icon University of Maryland, Baltimore County
  • 8. NSF NCAR Earth Observing Laboratory, Boulder, Colorado 80307, United States.
  • 9. ROR icon Goddard Space Flight Center

Abstract

Despite ongoing reductions in emissions of ozone (O3) precursors, nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs), the three largest urban areas in the United States ─ New York City (NYC), Chicago, and Los Angeles (LA) ─ continue to exceed national air quality standards for O3. Airborne measurements during the 2023 Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) campaign investigated nonlinear O3 photochemistry in these cities. We report mean ozone production efficiency (OPE), the enhancement ratio of Ox (= O3 + NO2) to NOx oxidation products, of 9 ± 4 (1σ), 6 ± 3, and 6 ± 3 ppbv ppbv–1 in NYC, Chicago, and LA, respectively. Compared to historical values, OPE has increased in NYC but remains constant in LA. We find that OPE during AEROMMA has a nonlinear, inverse relationship with total reactive nitrogen (NOy, a proxy for initial NOx) and a positive correlation with the nonmethane VOC to NOy enhancement ratio. A zero-dimensional photochemical model supports these observed OPE dependences on NOx and VOCs and shows that OPE is a distinct metric from total O3 production that is informative to the development of O3 pollution control strategies. We find that OPE values have higher variability, and a larger increase with NOx emissions reductions, in areas that experience NOx-sensitive rather than NOx-saturated O3 photochemistry; nonetheless, NOx reductions under NOx-sensitive conditions still reduce total O3 production despite the corresponding increase in OPE.

Copyright and License

© 2025 The Authors. Published by American Chemical Society.

This publication is licensed under CC-BY-NC-ND 4.0 .

Acknowledgement

The authors acknowledge the NOAA NESDIS Geostationary Extended Observations (GeoXO) Program for its support of AEROMMA flight operations. W.S.C., K.H.B., C.M.J., J.P., I.P., M.A.R., N.B.S., M.S., V.T., E.W., L.X., and K.Z. were partially supported by the NOAA Cooperative Agreement with CIRES, NA22OAR4320151. W.S.C. also received support from the University of Colorado Boulder Marion L. Sharrah Fellowship. G.I.G. was supported by the Klaus Tschira Boost Fund, a joint initiative of the German Scholars Organization and the Klaus Tschira Stiftung (grant no. KT28), and the European Research Council (ERC) under the European Union’s Horizon 2022 research and innovation program (Grant agreement No. 101076276). G.M.W. acknowledges support from NOAA AC4 grant NA21OAR4310138-T1-01 and the NASA Tropospheric Composition program.

Supplemental Material

Text, figures, and tables containing additional descriptions of instrumentation, analysis methods, box model setup, and results (PDF)

Files

chace-et-al-2025-ozone-production-efficiencies-in-the-three-largest-united-states-cities-from-airborne-measurements.pdf

Files (26.6 MB)

Additional details

Identifiers

PMID
40555410
PMCID
PMC12243090

Related works

Describes
Journal Article: 40555410 (PMID)
Journal Article: PMC12243090 (PMCID)
Is supplemented by
Supplemental Material: https://pubs.acs.org/doi/suppl/10.1021/acs.est.5c02073/suppl_file/es5c02073_si_001.pdf (URL)

Funding

National Oceanic and Atmospheric Administration
NA22OAR4320151
University of Colorado Boulder Marion L. Sharrah Fellowship
Klaus Tschira Boost Fund
KT28
Klaus Tschira Foundation
KT28
European Research Council
101076276
National Oceanic and Atmospheric Administration
NA21OAR4310138-T1-01
NASA Tropospheric Composition program

Dates

Accepted
2025-06-04
Available
2025-06-24
Published

Caltech Custom Metadata

Caltech groups
Division of Engineering and Applied Science (EAS), Division of Geological and Planetary Sciences (GPS)
Publication Status
Published