Preprints
https://doi.org/10.5194/acp-2021-786
https://doi.org/10.5194/acp-2021-786

  21 Sep 2021

21 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Changes of Anthropogenic Precursor Emissions Drive Shifts of Ozone Seasonal Cycle throughout Northern Midlatitude Troposphere

Henry Bowman1, Steven Turnock2,3, Susanne E. Bauer4,5, Kostas Tsigaridis4,5, Makoto Deushi6, Naga Oshima6, Fiona M. O'Connor2, Larry Horowitz7, Tongwen Wu8, Jie Zhang8, and David D. Parrish9 Henry Bowman et al.
  • 1Carleton College, Northfield, MN, 55057, USA
  • 2Met Office Hadley Centre, Exeter, UK
  • 3University of Leeds Met Office Strategic (LUMOS) Research Group, School of Earth and Environment, University of Leeds, UK
  • 4NASA Goddard Institute for Space Studies, New York, NY, USA
  • 5Center for Climate Systems Research, Columbia University, New York, NY, USA
  • 6Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki, 305-0052, Japan
  • 7NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, 08450, USA
  • 8Beijing Climate Center, China Meteorological Administration, Beijing, China
  • 9David.D.Parrish LLC, Boulder, CO, 80303, USA

Abstract. Simulations by six CMIP6 Earth System Models indicate that the seasonal cycle of baseline tropospheric ozone at northern midlatitudes has been shifting since the mid-20th Century. Beginning in ~ 1940 the seasonal cycle increased in amplitude by ~ 10 ppb (measured from seasonal minimum to maximum), and the seasonal maximum shifted to later in the year by about 3 weeks. This shift maximized in the mid-1980s, followed by a reversal – the seasonal cycle decreased in amplitude and the maximum shifted back to earlier in the year. Similar changes are seen in measurements collected from the 1970s to the present. The timing of the seasonal cycle changes is generally concurrent with the rise and fall of anthropogenic emissions that followed industrialization and subsequent implementation of air quality emission controls. We quantitatively compare the temporal changes of the ozone seasonal cycle at sites in both Europe and North America with the temporal changes of ozone precursor emissions across the northern midlatitudes and find a high degree of similarity between these two temporal patterns. We hypothesize that changing precursor emissions are responsible for the shift in the ozone seasonal cycle, and suggest the mechanism by which changing emissions drive the changing seasonal cycle: increasing emissions of NOX allow summertime photochemical production of ozone to become more important than ozone transported from the stratosphere and increasing VOCs lead to progressively greater photochemical ozone production in the summer months, thereby increasing the amplitude of the seasonal ozone cycle. Decreasing emissions of both precursor classes then reverse these changes. The quantitative parameter values that characterize the seasonal shifts provide useful benchmarks for evaluating model simulations, both against observations and between models.

Henry Bowman et al.

Status: open (until 10 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-786', Anonymous Referee #1, 12 Oct 2021 reply

Henry Bowman et al.

Henry Bowman et al.

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Short summary
A full understanding of ozone in the troposphere, requires investigation of its temporal variability over all time scales. Model simulations show that the northern midlatitude ozone seasonal cycle shifted with industrial development (1850–2014), with an increasing magnitude and a later summer peak. That shift reached a maximum in the mid-1980s, followed by a reversal toward the preindustrial cycle. The few available observations, beginning in the 1970s, are consistent with the model simulations.
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