Atmos. Chem. Phys. Discuss., 9, 1447-1487, 2009
www.atmos-chem-phys-discuss.net/9/1447/2009/
doi:10.5194/acpd-9-1447-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Impact of stratospheric intrusions and intercontinental transport on ozone at Jungfraujoch in 2005: comparison and validation of two Lagrangian approaches
J. Cui1, M. Sprenger1, J. Staehelin1, A. Siegrist1, M. Kunz1, S. Henne2, and M. Steinbacher2
1Institute for Atmospheric and Climate Science, ETH Zürich, Switzerland
2Laboratory for Air Pollution and Environmental Technology, EMPA, Dübendorf, Switzerland

Abstract. 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. It is also shown that although the long-range transported air is characterized by relatively low NOy/CO ratios and elevated CO concentrations, using a combination of NOy/CO and CO as control parameters still encounters difficulty in distinguishing 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 sustaining time longer than 12 h.

Citation: Cui, J., Sprenger, M., Staehelin, J., Siegrist, A., Kunz, M., Henne, S., and Steinbacher, M.: Impact of stratospheric intrusions and intercontinental transport on ozone at Jungfraujoch in 2005: comparison and validation of two Lagrangian approaches, Atmos. Chem. Phys. Discuss., 9, 1447-1487, doi:10.5194/acpd-9-1447-2009, 2009.
 
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