Abstract. During summer 1997, speciated reactive nitrogen (NO, NO2, peroxyacetyl nitrate (PAN), HNO3, and particulate nitrate) was measured in conjunction with total reactive nitrogen (NOv) at the high-alpine research station Jungfraujoch (JFJ), 3580 m above sea level (asl). The individually measured NO v components averaged to 82% of total NO v . PAN was the most abundant reactive nitrogen compound and composed on average 36% of NOv, followed by NOx (22%), particulate nitrate (17%), and HNO 3 (7%). The NOx/NOy ratio averaged 0.25, but significantly lower values (0.15-0.20) were observed in the presence of high NO v mixing ratios. A classification of the data by synoptic weather conditions indicated that thermally driven vertical transport has a strong impact on the mixing ratios measured at the JFJ during summer. A strong diurnal cycle with maximum mixing ratios in the late afternoon was observed for convective days with north-westerly advection at 500 hPa. In contrast, during a period of convective days with a wind speed below 7.5 m s -• at 500 hPa, no obvious diurnal cycle was observed. Under these meteorological conditions the convective boundary layer can be significantly higher over the Alps (i.e., around 4 km asl) than over the surrounding lowlands. Subsequent advection may finally result in the export of reactive nitrogen reservoir compounds to the free troposphere and hence influence global atmospheric chemistry.

The influence of meteorological transport processes on trace gas concentrations at the high-Alpine site Jungfraujoch (3580 m above sea level) is investigated. These processes are subdivided into two categories: thermally driven transport, which takes place on a local scale, and transport on a regional (f6hn) or synoptic scale (fronts). During thermally induced processes, which are mainly observed in summer and spring, the carbon monoxide (CO) mixing ratios show a diurnal variation with a maximum concentration at •1800 local time. Processes on the regional and synoptic scale which occur during the whole season induce large variability in the trace gas observations. The CO concentrations can be twice as large as the monthly median value during severe f6hn episodes. The NO x values exhibit an even larger increase. Depending on the season, the O3 observations during these periods show an increase in summer and a pronounced decrease in winter. In addition, it is found that the calculated trajectories using the output of a mesoscale weather prediction model are a useful tool to detect and explain episodes with high NO x or CO concentrations. Altogether, the present results imply that meteorological transport processes on different spatial and timescales are important for the interpretation of the trace gas observations at the high-Alpine site Jungfraujoch during the whole year.