Articles | Volume 9, issue 14
Atmos. Chem. Phys., 9, 5027–5042, 2009

Special issue: EMEP – an integrated system of models and observations...

Atmos. Chem. Phys., 9, 5027–5042, 2009

  27 Jul 2009

27 Jul 2009

The influence of foreign vs. North American emissions on surface ozone in the US

D. R. Reidmiller1,2, A. M. Fiore3, D. A. Jaffe2, D. Bergmann4, C. Cuvelier5, F. J. Dentener5, B. N. Duncan*,6, G. Folberth7, M. Gauss8, S. Gong9, P. Hess10, J. E. Jonson11, T. Keating12, A. Lupu13, E. Marmer5, R. Park14,***, M. G. Schultz15, D. T. Shindell16, S. Szopa17, M. G. Vivanco18, O. Wild19, and A. Zuber20 D. R. Reidmiller et al.
  • 1University of Washington, Department of Atmospheric Sciences, Seattle, WA, USA
  • 2University of Washington – Bothell, Department of Interdisciplinary Arts and Sciences, Bothell, WA, USA
  • 3NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
  • 4Atmospheric Earth and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA, USA
  • 5European Commission, Joint Research Centre JRC, Institute for Environment and Sustainability, Ispra, Italy
  • 6Goddard Earth Sciences {&} Technology Center, UMBC, MD, USA
  • 7Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
  • 8Department of Geosciences, University of Oslo, Oslo, Norway
  • 9Science and Technology Branch, Environment Canada, Toronto, ON, Canada
  • 10National Center for Atmospheric Research, Boulder, CO, USA
  • 11Norwegian Meteorological Institute, Oslo, Norway
  • 12Office of Policy Analysis and Review, EPA, Washington, DC, USA
  • 13Center for Research in Earth and Space Science, York University, Toronto, ON, Canada
  • 14Atmospheric Chemistry Modeling Group, Harvard University, Cambridge, MA, USA
  • 15ICG-2, Forschungszentrum Jülich, Jülich, Germany
  • 16NASA Goddard Institute for Space Studies and Columbia University, New York, NY, USA
  • 17Laboratoire des Sciences du Climat et de l'Environnement, CEA/CNRS/UVSQ/IPSL, Gif-sur-Yvette, France
  • 18Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
  • 19Lancaster Environment Centre, Lancaster University, Lancaster, UK
  • 20Environment Directorate General, European Commission, Brussels, Belgium
  • *now at: NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • **also at: Cornell University, Ithaca, New York, USA
  • ***now at: Seoul National University, Seoul, Korea

Abstract. As part of the Hemispheric Transport of Air Pollution (HTAP; http:// project, we analyze results from 15 global and 1 hemispheric chemical transport models and compare these to Clean Air Status and Trends Network (CASTNet) observations in the United States (US) for 2001. Using the policy-relevant maximum daily 8-h average ozone (MDA8 O3) statistic, the multi-model ensemble represents the observations well (mean r2=0.57, ensemble bias = +4.1 ppbv for all US regions and all seasons) despite a wide range in the individual model results. Correlations are strongest in the northeastern US during spring and fall (r2=0.68); and weakest in the midwestern US in summer (r2=0.46). However, large positive mean biases exist during summer for all eastern US regions, ranging from 10–20 ppbv, and a smaller negative bias is present in the western US during spring (~3 ppbv). In nearly all other regions and seasons, the biases of the model ensemble simulations are ≤5 ppbv. Sensitivity simulations in which anthropogenic O3-precursor emissions (NOx + NMVOC + CO + aerosols) were decreased by 20% in four source regions: East Asia (EA), South Asia (SA), Europe (EU) and North America (NA) show that the greatest response of MDA8 O3 to the summed foreign emissions reductions occurs during spring in the West (0.9 ppbv reduction due to 20% emissions reductions from EA + SA + EU). East Asia is the largest contributor to MDA8 O3 at all ranges of the O3 distribution for most regions (typically ~0.45 ppbv) followed closely by Europe. The exception is in the northeastern US where emissions reductions in EU had a slightly greater influence than EA emissions, particularly in the middle of the MDA8 O3 distribution (response of ~0.35 ppbv between 35–55 ppbv). EA and EU influences are both far greater (about 4x) than that from SA in all regions and seasons. In all regions and seasons O3-precursor emissions reductions of 20% in the NA source region decrease MDA8 O3 the most – by a factor of 2 to nearly 10 relative to foreign emissions reductions. The O3 response to anthropogenic NA emissions is greatest in the eastern US during summer at the high end of the O3 distribution (5–6 ppbv for 20% reductions). While the impact of foreign emissions on surface O3 in the US is not negligible – and is of increasing concern given the recent growth in Asian emissions – domestic emissions reductions remain a far more effective means of decreasing MDA8 O3 values, particularly those above 75 ppb (the current US standard).

Final-revised paper