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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-9-3371-2009</article-id>
<title-group>
<article-title>Impact of stratospheric intrusions and intercontinental transport on ozone at Jungfraujoch in 2005: comparison and validation of two Lagrangian approaches</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Cui</surname>
<given-names>J.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Sprenger</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Staehelin</surname>
<given-names>J.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Siegrist</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kunz</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Henne</surname>
<given-names>S.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Steinbacher</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Institute for Atmospheric and Climate Science, ETH Zürich, Switzerland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Laboratory for Air Pollution and Environmental Technology, EMPA, Dübendorf, Switzerland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>26</day>
<month>05</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>10</issue>
<fpage>3371</fpage>
<lpage>3383</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-chem-phys.net/9/3371/2009/acp-9-3371-2009.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/3371/2009/acp-9-3371-2009.pdf</self-uri>
<abstract>
<p>The particle dispersion model FLEXPART and the trajectory model LAGRANTO are
Lagrangian models which are widely used to study synoptic-scale atmospheric
air flows such as stratospheric intrusions (SI) and intercontinental
transport (ICT). In this study, we focus on SI and ICT events particularly
from the North American planetary boundary layer for the Jungfraujoch (JFJ)
measurement site, Switzerland, in 2005. Two representative cases of SI and
ICT are identified based on measurements recorded at Jungfraujoch and are
compared with FLEXPART and LAGRANTO simulations, respectively. Both models
well capture the events, showing good temporal agreement between models and
measurements. In addition, we investigate the performance of FLEXPART and
LAGRANTO on representing SI and ICT events over the entire year 2005 in a
statistical way. We found that the air at JFJ is influenced by SI during 19%
(FLEXPART) and 18% (LAGRANTO), and by ICT from the North American planetary
boundary layer during 13% (FLEXPART) and 12% (LAGRANTO) of the entire year.
Through intercomparsion with measurements, our findings suggest that both
FLEXPART and LAGRANTO are well capable of representing SI and ICT events if
they last for more than 12 h, whereas both have problems on representing
short events. For comparison with in-situ observations we used O&lt;sub&gt;3&lt;/sub&gt; and
relative humidity for SI events. As parameters to trace ICT events we used a
combination of NO&lt;sub&gt;y&lt;/sub&gt;/CO and CO, however these parameters are not
specific enough to distinguish aged air masses by their source regions.
Moreover, a sensitivity study indicates that the agreement between models and
measurements depends significantly on the threshold values applied to the
individual control parameters. Generally, the less strict the thresholds are,
the better the agreement between models and measurements. Although the
dependence of the agreement on the threshold values is appreciable, it
nevertheless confirms the conclusion that both FLEXPART and LAGRANTO are well
able to capture SI and ICT events with duration longer than 12 h.</p>
</abstract>
<counts><page-count count="13"/></counts>
</article-meta>
</front>
<body/>
<back>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1</label><mixed-citation publication-type="other" xlink:type="simple"> Auvray, M. and Bey, I.: Long-range transport to Europe: seasonal variations and implications for the European ozone budget, J. Geophys. Res., 110, D11303, \doi10.1029/2004JD005503, 2005. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Berntsen, T., Karlsdóttir, S., and Jaffe, D.: Asian emissions on the composition of air reaching the North Western United States, Geophys. Res. Lett., 26, 2171–2174, 1999. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Bourqui, M. S.: Stratosphere-troposphere exchange from the Lagrangian perspective: a case study and method sensitivities, Atmos. Chem. Phys., 6, 2651–2670, 2006. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Brioude, J., Cooper, O. R., Trainer, M., Ryerson, T. B., Holloway, J. S., Baynard, T., Peischl, J., Warneke, C., Neuman, J. A., De Gouw, J., Stohl, A., Eckhardt, S., Frost, G. J., McKeen, S. A., Hsie, E.-Y., Fehsenfeld, F. C., and Nédélec, P.: Mixing between a stratospheric intrusion and a biomass burning plume, Atmos. Chem. Phys., 7, 4229–4235, 2007. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Brunnekreef, B. and Holgate, S.: Air pollution and health, Lancet, 360, 1233–1242, 2002. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Chameides, W. and Walker, J.: A photochemical theory of tropospheric ozone, J. Geophys. Res., 78, 8751–8760, 1973. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Collins, W., Derwent, R., Garnier, B., Johnson, C., Sanderson, M., and Stevenson, D.: Effect of stratosphere-troposphere exchange on the future tropospheric ozone trend, J. Geophys. Res., 108, 8528, \doi10.1029/2002JF002617, 2003. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Cristofanelli, P., Bonasoni, P., Collins, W., Feichter, J., Forster, C., James, P., Kentarchos, A., Kubik, P., Land, C., Meloen, J., Roelofs, G., Siegmund, P., Sprenger, M., Schnabel, C., Stohl, A., Tobler, L., Tositti, L., Trickl, T., and Zanis, P.: Stratosphere-to-troposphere transport: A model and method evaluation, J. Geophys. Res., 108, 8525, \doi10.1029/2002JD002600, 2003. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Crutzen, P.: Photochemical reactions initiated by and influencing ozone in the unpolluted troposphere, Tellus, 26, 47–57, 1974. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Danielsen, E.: Stratospheric-tropospheric exchange based on radioactivity, ozone and potential vorticity, J. Atmos. Sci., 25, 502–518, 1968. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Eckhardt, S., Stohl, A., Beirle, S., Spichtinger, N., James, P., Forster, C., Junker, C., Wagner, T., Platt, U., and Jennings, S. G.: The North Atlantic Oscillation controls air pollution transport to the Arctic, Atmos. Chem. Phys., 3, 1769–1778, 2003. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Eckhardt, S., Stohl, A., Wernli, H., James, P., Forster, C., and Spichtinger, N.: A 15-year climatology of warm conveyor belts, J. Climate, 17, 218–237, 2004. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> Forster, C., Cooper, O., Stohl, A., Eckhardt, S., James, P., Dunlea, E., Nicks~Jr., D., Holloway, J., Hübler, G., Parrish, D., Ryerson, T., and Trainer, M.: Lagrangian transport model forecasts and a transport climatology for the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) measurement campaign, J. Geophys. Res., 109, D07S92, \doi10.1029/2003JD003589, 2004. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Gerasopoulos, E., Zanis, P., Papastefanou, C., Zerefos, C. S., Ioannidou, A., and Wernli, H.: Deep stratosphere-to-troposphere transport (STT) over SE Europe: a complex case study captured by enhanced $^7$Be concentrations at the surface of a low topography region, Atmos. Chem. Phys. Discuss., 5, 101–129, 2005. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Guerova, G., Bey, I., Attié, J.-L., Martin, R. V., Cui, J., and Sprenger, M.: Impact of transatlantic transport episodes on summertime ozone in Europe, Atmos. Chem. Phys., 6, 2057–2072, 2006. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple"> Holton, J., Haynes, P., McIntyre, M., Douglass, A., Rood, R., and Pfister, L.: Stratosphere-troposphere exchange, Rev. Geophys., 33, 403–439, 1995. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Hsu, J. and Prather, M.: Diagnosing the stratosphere-to-troposphere flux of ozone in a chemistry transport model, J. Geophys. Res., 110, D19305, \doi10.1029/2005JD006045, 2005. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Huntrieser, H., Heland, J., Schlager, H., Forster, C., Stohl, A., Aufmhoff, H., Arnold, F., Scheel, H., Campana, M., Gilge, S., Eixmann, R., and Cooper, O.: Intercontinental air pollution transport from North America to Europe: Experimental evidence from airborne measurements and surface observations, J. Geophys. Res., 110, D01305, \doi10.1029/2004JD005045, 2005. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> IPCC: Climate Change 2007: The Physical Scientific Basis, \mboxContribution of Working Group I to the Third Assessment Report of the Intergovermental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Jacob, D., Logan, J., and Murti, P.: Effect of rising Asian emissions on surface ozone in the United States, Geophys. Res. Lett., 26, 2175–2178, 1999. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> James, P., Stohl, A., Forster, C., Eckhardt, S., Seibert, P., and Frank, A.: A 15-year climatology of stratosphere-troposphere exchange with a Lagrangian particle dispersion model: 1. Methodology and validation, J. Geophys. Res., 108, 8519, \doi10.1029/2002JD002637, 2003a. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple"> James, P., Stohl, A., Forster, C., Eckhardt, S., Seibert, P., and Frank, A.: A 15-year climatology of stratosphere-troposphere exchange with a Lagrangian particle dispersion model: 2. Mean climate and seasonal variability, J. Geophys. Res., 108, 8522, \doi10.1029/2002JD002639, 2003b. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple"> Jonson, J., Sundet, J., and Tarrasón, L.: Model calculations of present and future levels of ozone and ozone precursors with a global and a regional model, Atmos. Environ., 35, 525–537, 2001. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Junge, C.: Global ozone budget and exchange between stratosphere and troposphere, Tellus, 14, 363–377, 1962. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Levy, H.: Large radical and formaldehyde concentrations predicted, Science, 173, 141–143, 1971. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Li, Q., Jacob, D., Palmer, P., Duncan, B., Field, B., Martin, R., Fiore, A., Yantosca, R., Parrish, D., Simmonds, P., and Oltmans, S.: Transatlantic transport of pollution and its effects on surface ozone in Europe and North America, J. Geophys. Res., 107, 4166, \doi10.1029/2001JD001422, 2002. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Li, Y., Campana, M., Reimann, S., Schaub, D., Stemmler, K., Staehelin, J., and Peter, T.: Hydrocarbon concentrations at the Alpine mountain sites Jungfraujoch and Arosa, Atmos. Environ., 39, 1113–1127, 2005. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Liu, S., Trainer, M., Fehsenfeld, F., Parrish, D., Williams, E., Fahey, D., Hübler, G., and Murphy, P.: Ozone production in the rural troposphere and the implications for regional and global ozone distributions, J. Geophys. Res., 92, 4191–4207, 1987. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> Olivier, J. and Berdowski, J.: Global emission sources and sinks, in: The Climate System, edited by: Berdowski, J., Guicherit, R., Heij, B. J., and Balkema, A. A., Publishers/Swets and Zeitlinger Publishers, Lisse, The Netherlands, iSBN 90 5809 255 0, 2001. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Olivier, J., Berdowski, J., Peters, J., Bakker, J., Visschedijk, A., and Bloos, J.: Applications of EDGAR, Including a description of EDGAR 3.2: reference database with trend data for 1970–1995, RIVM report 773301001/NRP report 410200 051, RIVM, Bilthoven, 2002. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Olivier, J., van Aardenne, J., Dentener, F., Ganzeveld, L., and Peters, J.: Recent Trends in Global Greenhouse Gas Emissions: Regional Trends and Spatial Distribution of Key Sources, Non-CO$\rm_2$ Greenhouse Gases (NCGG-4), Millpress, Rotterdam, iSBN 90 5966 043 9, 2005. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple"> Ordóñez, C., Brunner, D., Staehelin, J., Hadjinicolaou, P., Pyle, J., Jonas, M., Wernli, H., and Prévôt, A.: Strong influence of lowermost stratospheric ozone on lower tropospheric background ozone changes over Europe, Geophys. Res. Lett., 34, L07805, \doi10.1029/2006GL029113, 2007. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Roelofs, G.-J. and Lelieveld, J.: Model study of the influence of cross-tropopause O$\rm_3$ transport on tropospheric O$\rm_3$ levels, Tellus, 49B, 38–55, 1997. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Seinfeld, J. and Pandis, S.: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, John Wiley and Sons, Inc., iSBN: 0-471-82857-2, 1998. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Spichtinger, N., Wenig, M., James, P., Wagner, T., Platt, U., and Stohl, A.: Satellite detection of a continental-scale plume of nitrogen oxide from boreal forest fires, Geophys. Res. Lett., 28, 4579–4582, 2001. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Staehelin, J., Thudium, J., Buehler, R., Volz-Thomas, A., and Graber, W.: Trends in surface ozone concentration at Arosa (Switzerland), Atmos. Environ., 28, 75–87, 1994. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A.: A 1-year Lagrangian &quot;climatology&quot; of airstreams in the Northern Hemisphere troposphere and lowermost stratosphere, J. Geophys. Res., 106, 7263–7279, 2001. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A. and Trickl, T.: A textbook example of long-range transport: Simultaneous observation of ozone maxima of stratospheric and North American origin in the free troposphere over Europe, J. Geophys. Res., 104, 30445–30462, 1999. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A., Hittenberger, M., and Wotawa, G.: Validation of the Lagrangian dispersion model FLEXPART against large scale tracer experiment data, Atmos. Environ., 32, 4245–4264, 1998. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A., Spichtinger, N., Bonasoni, P., Feldmann, H., Memmesheimer, M., Scheel, H., Trickl, T., Hübener, S., Ringer, W., and Mandl, M.: The influence of stratospheric intrusions on alpine ozone concentrations, Atmos. Environ., 34, 1323–1354, 2000. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A., Eckhardt, S., Forster, C., James, P., and Spichtinger, N.: On the pathways and timescales of intercontinental air pollution transport, J. Geophys. Res., 107, 4684, \doi10.1029/2001JD001396, 2002a. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A., Trainer, M., Ryerson, T., Holloway, J., and Parrish, D.: Export of NO$\rm_y$ from the North American boundary layer during 1996 and 1997 North Atlantic Regional Experiments, J. Geophys. Res., 107, 4131, \doi10.1029/2001JD000519, 2002b. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Stohl, A., Forster, C., Frank, A., Seibert, P., and Wotawa, G.: Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2, Atmos. Chem. Phys., 5, 2461-2474, 2005. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Sudo, K., Takahashi, M., and Akimoto, H.: Future changes in stratosphere-troposphere exchange and their impacts on future tropospheric ozone simulations, Geophys. Res. Lett., 30, 2256, \doi10.1029/2003GL018526, 2003. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Tarasick, D., Fioletov, V., Wardle, D., Kerr, J., and Davies, J.: Changes in the vertical distribution of ozone over Canada from ozonesondes: 1998–2001, J. Geophys. Res., 110, D02304, \doi10.1029/2004JD0004643, 2005. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Wernli, H. and Davies, H.: A Lagrangian-based analysis of extratropical cyclones. I: The method and some applications, Q. J. Roy. Meteor. Soc., 123, 467–489, 1997. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Wild, O. and Akimoto, H.: Intercontinental transport of ozone and its precursors in a three-dimensional global CTM, J. Geophys. Res., 106, 27729–27744, 2001. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> Wild, O., Pochanart, P., and Akimoto, H.: Trans-Eurasian transport of ozone and its precursors, J. Geophys. Res., 109, D11302, \doi10.1029/2003JD004501, 2004. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Yienger, J., Klonccki, A., Levy~II, H., Moxim, W., and Carmichael, G.: An evaluation of chemistry&apos;s role in the winter-spring ozone maximum found in the northern midlatitude free troposphere, J. Geophys. Res., 104, 3655–3667, 1999. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Zanis, P., Trickl, T., Stohl, A., Wernli, H., Cooper, O., Zerefos, C., Gaeggeler, H., Schnabel, C., Tobler, L., Kubik, P. W., Priller, A., Scheel, H. E., Kanter, H. J., Cristofanelli, P., Forster, C., James, P., Gerasopoulos, E., Delcloo, A., Papayannis, A., and Claude, H.: Forecast, observation and modelling of a deep stratospheric intrusion event over Europe, Atmos. Chem. Phys., 3, 763–777, 2003. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple"> Zellweger, C., Ammann, M., Buchmann, B., Hofer, P., Lugauer, M., Rüttimann, R., Streit, N., Weingartner, E., and Baltensperger, U.: Summertime NO$\rm_y$ speciation at the Jungfraujoch, 3580 m above sea level, Switzerland, J. Geophys. Res., 105, 6655–6667, 2000. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple"> Zellweger, C., Forrer, J., Hofer, P., Nyeki, S., Schwarzenbach, B., Weingartner, E., Ammann, M., and Baltensperger, U.: Partitioning of reactive nitrogen (NO&lt;sub&gt;y&lt;/sub&gt;) and dependence on meteorological conditions in the lower free troposphere, Atmos. Chem. Phys., 3, 779–796, 2003. </mixed-citation>
</ref>
</ref-list>
</back>
</article>