Impact of stratospheric intrusions and intercontinental transport on ozone at Jungfraujoch in 2005: comparison and validation of two Lagrangian approaches

Abstract

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. For comparison with in-situ observations we used O 3 and relative humidity for SI events. As parameters to trace ICT events we used a combination of NO y /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 Correspondence to: J. Cui (junbo.cui@env.ethz.ch) 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.

Tropospheric ozone seasonal and long-term variability as seen by lidar and surface measurements at the JPL-Table Mountain Facility, California

“…An additional source of ozone in the troposphere is the downward transport from the stratosphere, where ozone is much more abundant (Levy et al, 1985). At high elevation sites such as the Jet Propulsion Laboratory Table Mountain Facility in southern California (TMF hereafter), the effect of the boundary layer is very small, and ozone variability is expected to be driven by transport processes from the stratosphere or horizontal transport within the troposphere (Cui et al, 2009;Naja et al, 2003;Trickl et al, 2010).…”

Tropospheric ozone variations at the Nepal Climate Observatory-Pyramid (Himalayas, 5079 m a.s.l.) and influence of deep stratospheric intrusion events

“…Considering the high altitude of the measurement site (5079 m a.s.l. ), the values may appear low, if compared with the SI frequencies (ranging from 5% to 40%) inferred at high mountain stations located in Europe (with altitudes ranging from 2100 to 3800 m a.s.l., see Stohl et al, 2000;Cristofanelli et al, 2006;Cui et al, 2009;Trickl et al, 2010). It could indicate that the southern Himalayas is not among the world regions most affected by SI.…”

“…In particular, we decided to select as influenced by possible SI, the days for which at least one of the 14 back-trajectories ending in a vertical range extending up to 50 hPa from the NCO-P altitude showed PV>1.6 pvu, basing on the experience gained in the analysis of case studies of stratospheric intrusions at other high mountain stations (Cristofanelli et al, 2006;Cui et al, 2009) and at the NCO-P itself (Bonasoni et al, 2009). With the aim of minimize the fraction of wrong selections, the considered tracers were analysed in groups of two (or more) and only simultaneous identification have been retained for the analysis.…”

Chemical and physical influences on aerosol activation in liquid clouds: a study based on observations from the Jungfraujoch, Switzerland

“…Staudt et al, 2001;Liang et al, 2004;Yashiro et al, 2009;Zhang et al, 2006Zhang et al, , 2009Gilge et al, 2010), and therefore in this study they are used as indicators of the degree of influence of polluted air masses, in an attempt to determine whether this has an important effect on particle activation at the JFJ. Ozone at the JFJ may be influenced by stratospheric intrusions, but a modelling study (Cui et al, 2009) has suggested that this is the case for less than 20 % of the year, making such events relatively rare.…”