25 Mar 2022
25 Mar 2022
Status: this preprint is currently under review for the journal ACP.

Sources of Surface O3 in the UK: Tagging O3 within WRF-Chem

Johana Romero-Alvarez1,a,b,c, Aurelia Lupaşcu2, Douglas Lowe3, Alba Badia1,4, Scott Acher-Nicholls5, Steve R. Dorling1, Claire E. Reeves1, and Tim Butler2,6 Johana Romero-Alvarez et al.
  • 1School of Environmental Sciences, University of East Anglia, Norwich, UK
  • 2Institute for Advanced Sustainability Studies (IASS), Potsdam, Germany
  • 3Centre for Atmospheric Sciences, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
  • 4Institute of Environmental Science and Technology (ICTA), Universitat Autònoma de Barcelona, Barcelona, Spain
  • 5Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, UK
  • 6Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany
  • anow at: Department of Chemistry, University of Colorado Boulder, Boulder, USA
  • bnow at: Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, CO, USA
  • cnow at: NOAA Global Systems Laboratory (GSL), Boulder, CO, USA

Abstract. Tropospheric ozone (O3) concentrations are known to depend on a combination of hemispheric, regional, and local-scale processes. Estimates of how much O3 is produced locally vs. transported from further afield are essential in air quality management and regulatory policies. Here, a tagged-ozone mechanism within the WRF-Chem model is used to quantify the contributions to surface O3 in the UK from anthropogenic nitrogen oxide (NOx) emissions from inside and outside the UK during May–August 2015. The contribution of the different source regions to three regulatory O3 metrics is also examined. It is shown that model simulations predict the concentration and spatial distribution of domain-wide surface O3 with a mean bias of -3.7 ppbv. Anthropogenic NOx emissions from the UK and Europe account respectively for 13 % and 16 % of the monthly mean surface O3 in the UK, as the majority (71 %) of O3 comes from the hemispheric background. The north and the west of the UK experience the largest contributions from hemispheric O3 with peaks in May, whereas European and UK contributions are most significant in the east and south-east, intensifying towards June and July. It is demonstrated that more stringent emission controls over continental Europe, particularly in western Europe, would be necessary to improve health-related metrics, such as MDA8 O3 above 50 and 60 ppbv. Emission controls over larger areas, e.g., the northern hemisphere, are instead required to lessen the impacts on ecosystems as quantified by metrics such as the AOT40.

Johana Romero-Alvarez 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-2022-173', Anonymous Referee #1, 08 May 2022
  • RC2: 'Comment on acp-2022-173', Anonymous Referee #2, 17 May 2022

Johana Romero-Alvarez et al.

Johana Romero-Alvarez et al.


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Short summary
As ozone can be transported across countries, efficient air quality management and regulatory policies rely on the assessment of local ozone production vs. transport. In our study, we investigate the origin of surface ozone in the UK and the contribution of the different source regions to regulatory ozone metrics. It is shown that emissions controls over western Europe would be necessary to improve health-related metrics and over larger areas to reduce impacts on ecosystems.