Articles | Volume 12, issue 23
Atmos. Chem. Phys., 12, 11485–11504, 2012
Atmos. Chem. Phys., 12, 11485–11504, 2012

Research article 04 Dec 2012

Research article | 04 Dec 2012

Long-term changes in lower tropospheric baseline ozone concentrations at northern mid-latitudes

D. D. Parrish1, K. S. Law2, J. Staehelin3, R. Derwent4, O. R. Cooper5,1, H. Tanimoto6, A. Volz-Thomas7, S. Gilge8, H.-E. Scheel9, M. Steinbacher10, and E. Chan11 D. D. Parrish et al.
  • 1NOAA ESRL Chemical Sciences Division, 325 Broadway, Boulder, CO, USA
  • 2UPMC Univ. Paris 06, Univ. Versailles Saint-Quentin, CNRS/INSU, UMR8190, LATMOS/IPSL, Paris, France
  • 3Institute for Atmospheric and Climate Science, ETHZ, Universitätstrasse 16, 8092 Zürich, Switzerland
  • 4rdscientific, Newbury, Berkshire RG14 6LH, UK
  • 5CIRES, University of Colorado, Boulder, CO, USA
  • 6National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
  • 7IEK-8, Forschungszentrum Juelich, 52425 Juelich, Germany
  • 8Hohenpeissenberg Meteorological Observatory, German Meteorological Service (DWD), Hohenpeissenberg, Germany
  • 9Karlsruhe Institute of Technology, IMK-IFU, 82467 Garmisch-Partenkirchen, Germany
  • 10Swiss Federal Laboratories for Materials Science and Technology (EMPA), Duebendorf, Switzerland
  • 11Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada

Abstract. Changes in baseline (here understood as representative of continental to hemispheric scales) tropospheric O3 concentrations that have occurred at northern mid-latitudes over the past six decades are quantified from available measurement records with the goal of providing benchmarks to which retrospective model calculations of the global O3 distribution can be compared. Eleven data sets (ten ground-based and one airborne) including six European (beginning in the 1950's and before), three North American (beginning in 1984) and two Asian (beginning in 1991) are analyzed. When the full time periods of the data records are considered a consistent picture emerges; O3 has increased at all sites in all seasons at approximately 1% yr−1 relative to the site's 2000 yr mixing ratio in each season. For perspective, this rate of increase sustained from 1950 to 2000 corresponds to an approximate doubling. There is little if any evidence for statistically significant differences in average rates of increase among the sites, regardless of varying length of data records. At most sites (most definitively at the European sites) the rate of increase has slowed over the last decade (possibly longer), to the extent that at present O3 is decreasing at some sites in some seasons, particularly in summer. The average rate of increase before 2000 shows significant seasonal differences (1.08 ± 0.09, 0.89 ± 0.10, 0.85 ± 0.11 and 1.21 ± 0.12% yr−1 in spring, summer, autumn and winter, respectively, over North America and Europe).

Final-revised paper