Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 12, 2551-2566, 2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Mar 2012
Long-term in situ measurements of NOx and NOy at Jungfraujoch 1998–2009: time series analysis and evaluation
S. Pandey Deolal1, D. Brunner2, M. Steinbacher2, U. Weers1, and J. Staehelin1 1Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology, Zürich, Switzerland
2Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
Abstract. We present an analysis of the NOy (NOx + other oxidized species) measurements at the high alpine site Jungfraujoch (JFJ, 3580 m a.s.l.) for the period 1998–2009, which is the longest continous NOy data set reported from the lower free troposphere worldwide. Due to stringent emission control regulations, nitrogen oxides (NOx) emissions have been reduced significantly in Europe since the late 1980s as well as during the investigation period. However, the time series of NOy at JFJ does not show a consistent trend but a maximum during 2002 to 2004 and a decreasing tendency thereafter. The seasonal cycle of NOy exhibits a maximum in the warm season and a minimum in the cold months, opposite to measurements in the PBL, reflecting the seasonal changes in vertical transport and mixing. Except for summer, the seasonal mean NOx concentrations at JFJ show a high year-to-year variability which is strongly controlled by short episodic pollution events obscuring any long-term trends. The low variability in mean and median NOx values in summer is quite remarkable indicating rapid photochemical conversion of NOx to higher oxidized species (NOz) of the NOy family on a timescale shorter than the time required to transport polluted air from the boundary layer to JFJ. In order to evaluate the quality of the NOy data series, an in-situ intercomparison with a second collocated NOy analyzer with a separate inlet was performed in 2009–2010 which showed an overall agreement within 10% including all uncertainties and errors.

Citation: Pandey Deolal, S., Brunner, D., Steinbacher, M., Weers, U., and Staehelin, J.: Long-term in situ measurements of NOx and NOy at Jungfraujoch 1998–2009: time series analysis and evaluation, Atmos. Chem. Phys., 12, 2551-2566,, 2012.
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