This dataset consists of a vector layer (based on 1 by 1° grid), of modelled surface ozone concentrations (ppb). The values per cell are daily mean surface ozone for the period 6am – 6pm. The seasonal average has been calculated for the grassland growing season, for the period spanning mid-April to mid-July, for the UK and the USA, for 2018. Full details about this dataset can be found at https://doi.org/10.5285/4b0871a9-196a-48e1-a0c8-c5f53e17e9a7