Partitioning of reactive nitrogen (NOy) and dependence on meteorological conditions in the lower free troposphere

[摘要] Results of continuous nitrogen oxide (NO), nitrogen dioxide(NO₂), peroxyacetyl nitrate (PAN) and total reactive nitrogen (NO_y) measurements along with seasonal field campaignsof nitric acid (HNO₃) and particulate nitrate (NO₃^-)measurements are presented for a two-year period at the high-alpine research station Jungfraujoch(JFJ), 3580 m asl. The NO_y mixing ratio and partitioning is shown to stronglydepend on meteorological conditions. Knowledge of these meteorological transport processes allows discrimination betweenundisturbed (i.e. clean) and disturbed (i.e. influenced by regional pollution sources) free tropospheric (FT) conditions atthe JFJ. Median NO_y concentrations during undisturbed FT periods ranged from350 pptv (winter, December to February) to 581 pptv (spring, March to May). PAN was found to be thedominant NO_y species during spring and summer, whereas NO₂ was most abundant during autumn and winter. Particulatenitrate was found to contribute significantly to total NO_y during thermally induced vertical transport.Föhn events, synoptical lifting (e.g. fronts) and thermally induced verticaltransport resulted in mixing ratios up to 10 times higher at the JFJ compared to undisturbed FT conditions. Furthermore thismeteorological variability of the NO_y concentration and partitioning often dominated the seasonal variability. As aconsequence the use of filters at the JFJ (and other mountainous sites) is crucial for the interpretation of data from suchmeasurement sites. This study presents a further development of meteorological filters for the high-alpine siteJungfraujoch, which also could be modified and adapted to other mountainousmeasurement sites.

[学科分类] 大气科学