Photochemical Oxidant Model Application within the Framework of Control Strategy Development in the Dutch/German Programme Phoxa

Abstract The Dutch-German Programme PHOXA (Photochemical Oxidant and Acid Deposition Model Application in the Framework of Control Strategy Development) is concerned with photochemical oxidants and the deposition of acidifying species. Effective measures to reduce elevated ozone concentrations in Europe need transboun-dary strategies; its impact can only be evaluated by applying regional dispersion models which provide substantial support to the transboundary control strategies. The objective of PHOXA consists in the preparation of an instrumentation in order to evaluate abatement strategies for photochemical oxidants and acidifying pollutants with regard to their European-wide effect on air quality and deposition. For the treatment of photochemical oxidants the RTM-III model was used to investigate episodes of high ozone concentrations. The evaluation of the findings shows that the long range dispersion model RTM-III predicts temporal and spatial patterns of ozone reasonably well in rural areas but underpredicts the highest observed hourly ozone values in more industrialized areas. The evaluation of some broad emission scenarios for selected photochemical episodes supports the fact that the RTM-III model responds in an explainable way to changes in the emission input.