Drivers of ozone pollution in Europe

Kurzfassung

Tropospheric Ozone is an important source for the generation of the hydroxyl radical (OH), which is important for cleansing the atmosphere from many chemical species such as carbon monoxide and methane. Ozone, however, is also a strong oxidant causing health problems to humans and decreasing the yield rates of some plants. Further, ozone is a greenhouse gas, contributing to global warming. Two important source for tropospheric ozone exist, the downward transport from the stratosphere as well as the in situ production in the troposphere by reactions of precursors. This production is strongly non-linear and involves mainly nitrogen oxides, carbon monoxide and volatile organic compounds. These precursors have several anthropogenic (e.g. road traffic) and natural sources (e.g. lightning). Because of the non-linearity of the production, the contribution of the different sources to ozone can not be derived by the amount of emissions alone. Instead, complex model simulations are necessary,involving a detailed representation of the chemistry as well as additional diagnostics to calculate the contribution of the different emission sources. In our work we apply the MECO(n) model system. This system allows to nest several instances of the regional chemistry-climate model COSMO-CLM/MESSy into the global chemistry-climate model EMAC. The on-line coupling of both models allows for a highly consistent model chain with respect to the chemistry as well as the contribution diagnostics. We present results from simulations for the year 2008. We show that the production of ozone in the planetary boundary layer in Europe is mainly governed by emissions from anthropogenic sources, as well as biogenic emissions (mainly nitrogen oxides from soils and isopren from plants). Further, the impact of ozone from the stratosphere as well as ozone transported over long range are discussed.