Articles | Volume 18, issue 3
Atmos. Chem. Phys., 18, 2341–2361, 2018
Atmos. Chem. Phys., 18, 2341–2361, 2018

Research article 16 Feb 2018

Research article | 16 Feb 2018

Decadal changes in summertime reactive oxidized nitrogen and surface ozone over the Southeast United States

Jingyi Li1, Jingqiu Mao2, Arlene M. Fiore3, Ronald C. Cohen4,5, John D. Crounse6, Alex P. Teng6, Paul O. Wennberg6,7, Ben H. Lee8, Felipe D. Lopez-Hilfiker8, Joel A. Thornton8, Jeff Peischl9,10, Ilana B. Pollack11, Thomas B. Ryerson9, Patrick Veres9,10, James M. Roberts9, J. Andrew Neuman9,10, John B. Nowak12,a, Glenn M. Wolfe13,14, Thomas F. Hanisco14, Alan Fried15, Hanwant B. Singh16, Jack Dibb17, Fabien Paulot18,19, and Larry W. Horowitz19 Jingyi Li et al.
  • 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 2Department of Chemistry and Biochemistry & Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
  • 3Department of Earth and Environmental Sciences & Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
  • 4Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
  • 5Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA
  • 6Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
  • 7Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA
  • 8Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USA
  • 9Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
  • 10Cooperative Institute for Research in Environmental Science, University of Colorado Boulder, Boulder, CO 80309, USA
  • 11Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA
  • 12Aerodyne Research, Inc., Billerica, MA 01821, USA
  • 13Joint Center for Earth System Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA
  • 14Atmospheric Chemistry and Dynamics Lab, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 15Institute of Arctic & Alpine Research, University of Colorado Boulder, Boulder, CO 80309, USA
  • 16NASA Ames Research Center, Moffett Field, CA 94035, USA
  • 17Department of Earth Sciences and Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA
  • 18Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ 08544, USA
  • 19Geophysical Fluid Dynamics Laboratory/National Oceanic and Atmospheric Administration, Princeton, NJ 08540, USA
  • anow at: NASA Langley Research Center, Hampton, VA 23681, USA

Abstract. Widespread efforts to abate ozone (O3) smog have significantly reduced emissions of nitrogen oxides (NOx) over the past 2 decades in the Southeast US, a place heavily influenced by both anthropogenic and biogenic emissions. How reactive nitrogen speciation responds to the reduction in NOx emissions in this region remains to be elucidated. Here we exploit aircraft measurements from ICARTT (July–August 2004), SENEX (June–July 2013), and SEAC4RS (August–September 2013) and long-term ground measurement networks alongside a global chemistry–climate model to examine decadal changes in summertime reactive oxidized nitrogen (RON) and ozone over the Southeast US. We show that our model can reproduce the mean vertical profiles of major RON species and the total (NOy) in both 2004 and 2013. Among the major RON species, nitric acid (HNO3) is dominant (∼ 42–45 %), followed by NOx (31 %), total peroxy nitrates (ΣPNs; 14 %), and total alkyl nitrates (ΣANs; 9–12 %) on a regional scale. We find that most RON species, including NOx, ΣPNs, and HNO3, decline proportionally with decreasing NOx emissions in this region, leading to a similar decline in NOy. This linear response might be in part due to the nearly constant summertime supply of biogenic VOC emissions in this region. Our model captures the observed relative change in RON and surface ozone from 2004 to 2013. Model sensitivity tests indicate that further reductions of NOx emissions will lead to a continued decline in surface ozone and less frequent high-ozone events.

Short summary
We present the first comprehensive model evaluation of summertime reactive oxidized nitrogen using a high-resolution chemistry–climate model with up-to-date isoprene oxidation chemistry, along with a series of observations from aircraft campaigns and ground measurement networks from 2004 to 2013 over the Southeast US. We investigate the impact of NOx emission reductions on changes in reactive nitrogen speciation and export efficiency as well as ozone in the past and future decade.
Final-revised paper