Experimental and Numerical Study of High Ozone Events in the Alpine-Region

In the alpine region as well as in other European areas the ozone concentration appears to be increasing (Warmbt, 1977). During this century the ozone levels in the atmospheric boundary layer have been almost doubled (Volz and Kley, 1988). After Puxbaum et al. (1991) the ozone concentration in the Zillertal (a small valley in the Austrian Alps) has been increased by a factor of 3 since 1950. Beside this long term trend high ozone values of 100 ppb and more are increasingly observed during pollution episodes. These episodes are associated with high pressure systems, when the meteorological condition, in particular warm temperatures, clear skies and low wind speeds, encourage the photochemical formation of ozone. Calms and inversions causing reduced ventilation occur more frequently in mountain valleys than over flat terrain (Dreiseitl and Weber, 1991). Therefore the meteorological conditions in the Alps conduce the ozone production.