Composition and Chemistry
North American influence on tropospheric ozone and the effects of recent emission reductions: Constraints from ICARTT observations
Article first published online: 4 APR 2009
Copyright 2009 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 114, Issue D7, 16 April 2009
How to Cite
2009), North American influence on tropospheric ozone and the effects of recent emission reductions: Constraints from ICARTT observations, J. Geophys. Res., 114, D07302, doi:10.1029/2008JD010126., , , , , , , , and (
- Issue published online: 4 APR 2009
- Article first published online: 4 APR 2009
- Manuscript Accepted: 21 JAN 2009
- Manuscript Revised: 30 DEC 2008
- Manuscript Received: 14 MAR 2008
- tropospheric ozone;
- ozone air quality
 We use observations from the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign over eastern North America in summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem), to improve and update estimates of North American influence on global tropospheric ozone and the effect of recent U.S. anthropogenic reductions on surface ozone pollution. We find that the 50% decrease in U.S. stationary NOx sources since 1999 has decreased mean U.S. boundary layer ozone concentrations by 6–8 ppbv in the southeast and 4–6 ppbv in the Midwest. The observed dO3/dCO molar enhancement ratio in the U.S. boundary layer during ICARTT was 0.46 mol mol−1, larger than the range of 0.3–0.4 from studies in the early 1990s, possibly reflecting the decrease in the NOx/CO emission ratio as well as an increase in the ozone production efficiency per unit NOx. North American NOx emissions during summer 2004 as constrained by the ICARTT observations (0.72 Tg N fossil fuel, 0.11 Tg N biomass burning, 0.28 Tg N lightning for 1 July to 15 August) enhanced the hemispheric tropospheric ozone burden by 12.4%, with comparable contributions from fossil fuel and lightning (5–6%), but only 1% from biomass burning emissions despite 2004 being a record fire year over Alaska and western Canada.