An ozone budget for the UK: using measurements from the national ozone monitoring network; measured and modelled meteorological data, and a ‘big-leaf’ resistance analogy model of dry deposition

Data from the UK national air-quality monitoring network are used to calculate an annual mass budget for ozone (O3) production and loss in the UK boundary layer during 1996. Monthly losses by dry deposition are quantified from 1 km×1 km scale maps of O3 concentration and O3 deposition velocities based on a ‘big-leaf’ resistance analogy. The quantity of O3 deposition varies from 50 Gg-O3 month−1 in the winter to over 200 Gg-O3 month−1 in the summer when vegetation is actively absorbing O3. The net O3 production or loss in the UK boundary layer is found by selecting days when the UK is receiving “clean” Atlantic air from the SW to NW. In these conditions, the difference in O3 concentration observed at Mace Head and a rural site on the east coast of the UK indicates the net O3 production or loss within the UK boundary layer. A simple box model is then used to convert the concentration difference into a mass. The final budget shows that for most of the year the UK is a net sink for O3 (−25 to −800 Gg-O3 month−1) with production only exceeding losses in the photochemically active summer months (+45 Gg-O3 month−1).