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Why do models overestimate surface ozone in the Southeast United States?

Travis, Katherine R. and Jacob, Daniel J. and Fisher, Jenny A. and Kim, Patrick S. and Marais, Eloise A. and Zhu, Lei and Yu, Karen and Miller, Christopher C. and Yantosca, Robert M. and Sulprizio, Melissa P. and Thompson, Anne M. and Wennberg, Paul O. and Crounse, John D. and St. Clair, Jason M. and Cohen, Ronald C. and Laughner, Joshua L. and Dibb, Jack E. and Hall, Samuel R. and Ullmann, Kirk and Wolfe, Glenn M. and Pollack, Illana B. and Peischl, Jeff and Neuman, Jonathan A. and Zhou, Xianliang (2016) Why do models overestimate surface ozone in the Southeast United States? Atmospheric Chemistry and Physics, 16 (21). pp. 13561-13577. ISSN 1680-7324. PMCID PMC5880041.

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Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NO_x  ≡  NO + NO_2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC^4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°  ×  0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NO_x from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC^4RS observations of NO_x and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO_2 columns. Our results indicate that NEI NO_x emissions from mobile and industrial sources must be reduced by 30–60 %, dependent on the assumption of the contribution by soil NO_x emissions. Upper-tropospheric NO_2 from lightning makes a large contribution to satellite observations of tropospheric NO_2 that must be accounted for when using these data to estimate surface NO_x emissions. We find that only half of isoprene oxidation proceeds by the high-NO_x pathway to produce ozone; this fraction is only moderately sensitive to changes in NO_x emissions because isoprene and NO_x emissions are spatially segregated. GEOS-Chem with reduced NO_x emissions provides an unbiased simulation of ozone observations from the aircraft and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NO_x oxidation products. However, the model is still biased high by 6 ± 14 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle
Travis, Katherine R.0000-0003-1628-0353
Jacob, Daniel J.0000-0002-6373-3100
Marais, Eloise A.0000-0001-5477-8051
Sulprizio, Melissa P.0000-0003-4641-5546
Wennberg, Paul O.0000-0002-6126-3854
Crounse, John D.0000-0001-5443-729X
St. Clair, Jason M.0000-0002-9367-5749
Cohen, Ronald C.0000-0001-6617-7691
Laughner, Joshua L.0000-0002-8599-4555
Dibb, Jack E.0000-0003-3096-7709
Hall, Samuel R.0000-0002-2060-7112
Ullmann, Kirk0000-0002-4724-9634
Wolfe, Glenn M.0000-0001-6586-4043
Pollack, Illana B.0000-0001-7151-9756
Peischl, Jeff0000-0002-9320-7101
Additional Information:© 2016 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Received: 03 Feb 2016 – Published in Atmos. Chem. Phys. Discuss.: 16 Mar 2016; Revised: 05 Oct 2016 – Accepted: 06 Oct 2016 – Published: 01 Nov 2016. We are grateful to the entire NASA SEAC4RS team for their help in the field. We thank Tom Ryerson for his measurements of NO and NO_2 from the NOAA NO_yO_3 instrument. We thank L. Gregory Huey for the use of his CIMS PAN measurements. We thank Fabien Paulot and Jingqiu Mao for their helpful discussions of isoprene chemistry. We thank Christoph Keller for his help in implementing the NEI11v1 emissions into GEOS-Chem. We acknowledge the EPA for providing the 2011 North American emission inventory and in particular George Pouliot for his help and advice. These emission inventories are intended for research purposes. A technical report describing the 2011 modeling platform can be found at A description of the 2011 NEI can be found at This work was supported by the NASA Earth Science Division and by STAR Fellowship Assistance Agreement no. 91761601-0 awarded by the US Environmental Protection Agency (EPA). It has not been formally reviewed by EPA. The views expressed in this publication are solely those of the authors. JAF acknowledges support from a University of Wollongong Vice Chancellor’s Postdoctoral Fellowship. This research was undertaken with the assistance of resources provided at the NCI National Facility systems at the Australian National University through the National Computational Merit Allocation Scheme supported by the Australian Government.
Funding AgencyGrant Number
Environmental Protection Agency (EPA)UNSPECIFIED
University of WollongongUNSPECIFIED
Issue or Number:21
PubMed Central ID:PMC5880041
Record Number:CaltechAUTHORS:20161206-085019989
Persistent URL:
Official Citation:Travis, K. R., Jacob, D. J., Fisher, J. A., Kim, P. S., Marais, E. A., Zhu, L., Yu, K., Miller, C. C., Yantosca, R. M., Sulprizio, M. P., Thompson, A. M., Wennberg, P. O., Crounse, J. D., St. Clair, J. M., Cohen, R. C., Laughner, J. L., Dibb, J. E., Hall, S. R., Ullmann, K., Wolfe, G. M., Pollack, I. B., Peischl, J., Neuman, J. A., and Zhou, X.: Why do models overestimate surface ozone in the Southeast United States?, Atmos. Chem. Phys., 16, 13561-13577, doi:10.5194/acp-16-13561-2016, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72589
Deposited By: Tony Diaz
Deposited On:06 Dec 2016 19:40
Last Modified:09 Mar 2020 13:19

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