Preprints
https://doi.org/10.5194/acp-2020-1198
https://doi.org/10.5194/acp-2020-1198

  07 Jan 2021

07 Jan 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Anthropogenic Reversal of the Natural Ozone Gradient between Northern and Southern Mid-latitudes

David D. Parrish1, Richard G. Derwent2, Steven T. Turnock3, Fiona M. O’Connor3, Johannes Staehelin4, Susanne E. Bauer5,6, Makoto Deushi7, Naga Oshima7, Kostas Tsigaridis6,5, Tongwen Wu8, and Jie Zhang8 David D. Parrish et al.
  • 1David.D.Parrish, LLC, Boulder, CO, 80303, USA
  • 2rdscientific, Newbury, Berkshire, RG14 6LH, United Kingdom
  • 3Met Office Hadley Centre, Exeter, UK
  • 4ETH Zurich, Zurich, Switzerland
  • 5NASA Goddard Institute for Space Studies, New York, NY, USA
  • 6Center for Climate Systems Research, Columbia University, New York, NY, USA
  • 7Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki, 305-0052, Japan
  • 8Beijing Climate Center, China Meteorological Administration, Beijing, China

Abstract. Our quantitative understanding of natural tropospheric ozone concentrations is limited by the paucity of reliable measurements before the 1980s. We utilize the existing measurements to compare the long-term ozone changes that occurred within the marine boundary layer at northern and southern mid-latitudes. Since 1950 ozone concentrations have increased by a factor of 2.1 ± 0.2 in the northern hemisphere (NH) and are presently larger than in the southern hemisphere (SH), where only a much smaller increase has occurred. These changes are attributed to increased ozone production driven by anthropogenic emissions of photochemical ozone precursors that increased with industrial development. The greater ozone concentrations and increases in the NH are consistent with the predominant location of anthropogenic emission sources in that hemisphere. The available measurements indicate that this interhemispheric gradient was much smaller, and was likely reversed in the natural troposphere with higher concentrations in the SH. Six Earth System Model (ESM) simulations indicate similar total NH increases (1.9 with a standard deviation of 0.3), but they occurred more slowly over a longer time period, and the ESMs do not find higher pre-industrial ozone in the SH. Several uncertainties in the ESMs may cause these model-measurement disagreements: the assumed natural nitrogen oxide emissions may be too large, the relatively greater fraction of ozone injected by stratosphere-troposphere exchange to the NH may be overestimated, ozone surface deposition to ocean and land surfaces may not be accurately simulated, and model treatment of emissions of biogenic hydrocarbons and their photochemistry may not be adequate.

David D. Parrish et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1198', Laura Gallardo, 06 Feb 2021
    • AC1: 'Reply on RC1', David Parrish, 22 Mar 2021
  • RC2: 'Comment on acp-2020-1198', Anonymous Referee #1, 08 Feb 2021
    • RC3: 'Reply on RC2', Anonymous Referee #1, 08 Feb 2021
    • AC2: 'Reply on RC2', David Parrish, 22 Mar 2021
  • CC1: 'Comment on acp-2020-1198 by Cooper, Tarasick, Galbally and Schultz', Owen Cooper, 22 Feb 2021
    • AC3: 'Reply on CC1', David Parrish, 22 Mar 2021

David D. Parrish et al.

David D. Parrish et al.

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Short summary
The few ozone measurements made before the 1980s indicate that industrial development increased ozone concentrations by a factor of ~2 at northern mid-latitudes, which are now larger than at southern mid-latitudes. This difference was much smaller, and likely reversed, in the natural troposphere. Earth System Models find similar increases, but not higher pre-industrial ozone in the south. This disagreement may indicate that modeled natural ozone sources and/or deposition loss are inadequate.
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