Sources of surface O3 in the UK: tagging O3 within WRF-Chem
Journal Article
Overview
abstract
Abstract. Tropospheric ozone (O3) concentrations 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 Weather Research and Forecasting model coupled with chemistry (WRF-Chem) 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 surface O3 with a domain-wide; mean bias of −3.7 ppbv. Anthropogenic NOx emissions from the UK and Europe; account for 13 % and 16 %, respectively, of the monthly mean surface; O3 in the UK, as the majority (71 %) of O3 originates from the; hemispheric background. Hemispheric O3 contributes the most to; concentrations in the north and the west of the UK with peaks in May,; whereas European and UK contributions are most significant in the east,; south-east, and London, i.e. the UK's most populated areas, intensifying; towards June and July. Moreover, O3 from European sources is generally; transported to the UK rather than produced in situ. It is demonstrated that; more stringent emission controls over continental Europe, particularly in; western Europe, would be necessary to improve the health-related metric MDA8; O3 above 50 and 60 ppbv. Emission controls over larger areas, such as; the Northern Hemisphere, are instead required to lessen the impacts on; ecosystems as quantified by the AOT40 metric.;
