ASSESSING RECENT SURFACE OZONE CONCENTRATIONS IN THE UK

A 17-site national ozone monitoring network was established in 1987 by Warren Spring Laboratory and other organizations for the U.K. Department of the Environment. 1989 was the mast photochemically active year since the network commenced full operation. This paper therefore provides the first comprehensive analysis of U.K. ozone levels during such a period of interest. Although significantly greater numbers of photochemical episodes were observed in 1989 than in the previous 2 years, trend analysis of measurements from long-running sites over the last 15 years demonstrates that this year was not exceptional when viewed in a long-term context. Network data are here compared with the World Health Organization guidelines for ozone. All criteria examined are widely exceeded throughout the U.K., and in particular during photochemically active years such as 1989. Detailed spatial patterns of ozone concentrations throughout the U.K. are described for the first time: those for short term (hourly and and 8-hourly) concentrations show a clear north/south gradient every year since 1987. The patterns observed are consistent with broader features of ozone variation throughout continental Europe. Substantially different spatial patterns are observed when daily average concentrations are examined, with concentrations being highest in rural areas with low NOx emissions.