High-ozone layers in the middle and upper troposphere above Central Europe: strong import from the stratosphere over the Pacific Ocean

Abstract

Abstract. Very dry high-ozone layers have been repeatedly observed with the ozone lidar in Garmisch-Partenkirchen (Germany) starting one or two days after the onset of high-pressure periods during the warm season. These episodes have been analysed by trajectory calculations and extended simulations with the FLEXPART particle dispersion model. Mixed contributions from the stratosphere over the Pacific Ocean and the boundary layers of East Asia and North America were found. The stratospheric influence is mostly dominating and caused by a rather shallow transfer from the stratosphere into these rapid upper- and mid-tropospheric air streams. The considerable vertical extent of these layers and peak ozone mixing ratios between 80 and 150 ppb suggest an important mechanism for stratosphere-to-troposphere transport.

Forecasted deep stratospheric intrusions over Central Europe: case studies and climatologies

“…Therefore, we missed stratospheric air masses from either outside the ETH model domain or from inside the domain, but with a travel time of more than four days, do not enter our count if they overpass the station at altitudes high enough that there is no indication in the Zugspitze record. As shown in our long-range transport studies there may be considerable advection of thick aged air layers, rapidly travelling in the middle and upper troposphere, fed by STT events above the Pacific Ocean and Asia (Trickl et al, , 2009). …”

“…A first case study was published by Zanis et al (2003). In this study and in a companion paper on long-range advection of stratospheric air (Trickl et al, 2009) we give a more complete report of the results obtained in 2001 which cover a large variety of rather different situations.…”

“…The co-ordinated vertical sounding effort during that year, made possible by the daily forecasts, thus, offered a unique chance for a model validation. Two intrusion examples extracted from the run for 2001 are shown in this paper, one more also discussed in the companion paper (Trickl et al, 2009) is just briefly described. By comparison with the lidar measurements the quality of the simulations could be verified.…”

“…Some details have been evaluated with the FLEXPART tracer model (Stohl et al, 1998Stohl and Thomson, 1999), operated with ECMWF re-analysis data. This model has been extensively used for transport studies, in particular for several STT case studies of our team (Stohl and Trickl, 1999;Stohl et al, 2000;Trickl et al, 2003Trickl et al, , 2009Zanis et al, 2003).…”

“…3 were made in the retroplume mode described by Stohl et al (2002) and also in our parallel paper (Trickl et al, 2009). The backward plumes, calculated over twenty days, yield a more complete and reliable picture of the principal pathways of the air masses arriving at an observational site than conventional trajectory analyses since the full contour of the plume is obtained.…”