Document Type

Article

Publication Date

2016

Publication Title

Atmospheric Chemistry and Physics

ISSN

1680-7324

Volume

16

Issue

21

DOI

http://dx.doi.org/10.5194/acp-16-13561-2016

Abstract

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO+NO2) 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 SEAC4RS 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 NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30-60%, dependent on the assumption of the contribution by soil NOx emissions. Upper-tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx 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 NOx oxidation products. However, the model is still biased high by 6±14ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7ppb ozone decrease from 1.5km 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.

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AUTHORS

K. R. Travis (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) D. J. Jacob (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) D. J. Jacob (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA) J. A. Fisher (Centre for Atmospheric Chemistry, School of Chemistry, University of Wollongong, Wollongong, NSW, Australia) J. A. Fisher (School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, Australia) P. S. Kim (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA) E. A. Marais (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) L. Zhu (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) K. Yu (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) C. C. Miller (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) R. M. Yantosca (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) M. P. Sulprizio (Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA) A. M. Thompson (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA) P. O. Wennberg (Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA) P. O. Wennberg (Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA) J. D. Crounse (Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA) J. M. St. Clair (Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA) R. C. Cohen (Department of Chemistry, University of California, Berkeley, CA, USA) J. L. Laughner (Department of Chemistry, University of California, Berkeley, CA, USA) J. E. Dibb (Earth System Research Center, University of New Hampshire, Durham, NH, USA) S. R. Hall (Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA) K. Ullmann (Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA) G. M. Wolfe (Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA) G. M. Wolfe (Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD, USA) I. B. Pollack (Department of Atmospheric Science, Colorado State University, Colorado, USA) J. Peischl (University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA) J. Peischl (NOAA Earth System Research Lab, Boulder, CO, USA) J. A. Neuman (University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA) J. A. Neuman (NOAA Earth System Research Lab, Boulder, CO, USA) X. Zhou (Department of Environmental Health Sciences, State University of New York, Albany, New York 12201, USA) X. Zhou (Wadsworth Center, New York State Department of Health, Albany, New York, USA)

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