Tropospheric ozone in a global-scale three-dimensional Lagrangian model and its response to NOX emission controls

A three-dimensional Lagrangian tropospheric chemistry model is used to investigate the impact of human activities on the tropospheric distribution of ozone and hydroxyl radicals. The model describes the behaviour of 50 species including methane, carbon monoxide, oxides of nitrogen, sulphur dioxide and nine organic compounds emitted from human activities and a range of other sources. The chemical mechanism involves about 100 chemical reactions of which 16 are photochemical reactions whose diurnal dependence is treated in full. The model utilises a five minute chemistry time step and a three hour advection time step for the 50,000 air parcels. Meteorological data for the winds, temperatures, clouds and so on are taken from the UK Meteorological Office global model for 1994 onwards. The impacts of a 50% reduction in European NOX emissions on global ozone concentrations are assessed. Surface ozone concentrations decrease in summertime and rise in wintertime, but to different extents.