Measurements of ozone and peroxyacetyl nitrate (pan) in Munich

Simultaneous measurements of ozone and —for the first time in Munich—of PAN were carried out at two sites in the urban area of Munich during two periods (16 June–15 September 1989 and 1 January–30 April 1990). Maximum mixing ratios reached 75 ppbv for ozone (10-min-average) and 5.6 ppbv for PAN (20-min-value), respectively. Ozone showed more pronounced diurnal variations than PAN. In both cases they were related to diurnal variations of the global radiation and the mixing ratios of NO_x. Regarding ozone linear correlation analysis with meteorological parameters revealed distinct dependencies, especially on UV radiation, whereas the results for PAN reflected its more complicated formation. As far as dependencies on wind velocity are concerned, both ozone and PAN exhibited maximum mixing ratios in cases where the wind velocity was below 5 ms⁻¹. With increasing wind velocity both mixing ratios tended towards their natural background concentrations. Investigations concerning the influence of the wind direction did not disclose any particular local effects, but rather a relationship to the general weather situations. On the whole, PAN could be considered as a more characteristics indicator of smog conditions than ozone due to its low background concentrations and its thermal instability.