ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-3-763-2003 Forecast, observation and modelling of a deep stratospheric intrusion event over Europe Zanis P. 1 Trickl T. 2 Stohl A. 3 Wernli H. 4 Cooper O. 5 Zerefos C. 6 Gaeggeler H. 7 8 Schnabel C. 7 9 10 Tobler L. 8 Kubik P. W. 11 Priller A. 12 Scheel H. E. 2 Kanter H. J. 2 Cristofanelli P. 13 Forster C. 3 James P. 3 Gerasopoulos E. 14 Delcloo A. 15 Papayannis A. 16 Claude H. 17 Research Center for Atmospheric Physics and Climatology, Academy of Athens, Athens, Greece Forschungszentrum Karlsruhe, IMK-IFU, Garmisch-Partenkirchen, Germany Lehrstuhl für Bioklimatologie und Immissionsforschung Technische Universität München, Freising, Germany Atmospheric Physics, ETHZ, Zürich, Switzerland Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder/NOAA Aeronomy Laboratory, Boulder, USA Laboratory of Climatology and Atmospheric Environment, National and Kapodistrian University of Athens, Greece Departement für Chemie und Biochemie, Universität Bern, Switzerland Paul Scherrer Institute, Villigen PSI, Switzerland Inst. Particle Physics, ETH Hoenggerberg, Switzerland Scottish Universities Environmental Research Centre, East Kilbride, U.K. Paul Scherrer Institute, c/o ETH Hoenggerberg, Switzerland Institut für Isotopenforschung und Kernphysik, Universität Wien, Austria Institute of Atmospheric Sciences and Climate, Bologna, Italy Nuclear Physics Department, Aristotle Univ. of Thessaloniki, Greece Royal Meteorological Institute KMI, Uccle, Belgium Department of Physics, National Technical University of Athens, Greece Deutscher Wetterdienst, Meteorologisches Observatorium Hohenpeißenberg, Germany 18 06 2003 3 3 763 777 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. This article is available from http://www.atmos-chem-phys.net/3/763/2003/acp-3-763-2003.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/3/763/2003/acp-3-763-2003.pdf

A wide range of measurements was carried out in central and southeastern Europe within the framework of the EU project STACCATO (Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity) with the principle goal to create a comprehensive data set on stratospheric air intrusions into the troposphere along a rather frequently observed pathway over central Europe from the North Sea to the Mediterranean Sea. The measurements were based on predictions by suitable quasi-operational trajectory calculations using ECMWF forecast data. A predicted deep Stratosphere to Troposphere Transport (STT) event, encountered during the STACCATO period on 20-21 June 2001, was followed by the measurements network almost from its inception. Observations provide evidence that the intrusion affected large parts of central and southeastern Europe. Especially, the ozone lidar observations on 20-21 June 2001 at Garmisch-Partenkirchen, Germany captured the evolution of two marked tongues of high ozone with the first one descending to nearly 2 km, thus providing an excellent data set for model intercomparisons and validation. In addition, for the first time to our knowledge concurrent surface measurements of the cosmogenic radionuclides <sup>10</sup>Be and <sup>7</sup>Be and their ratio <sup>10</sup>Be/<sup>7</sup>Be are presented together as stratospheric tracers in a case study of a stratospheric intrusion. The ozone tracer columns calculated with the FLEXPART model were found to be in good agreement with water vapour satellite images, capturing the evolution of the observed dry streamers of stratospheric origin. Furthermore, the time-height cross section of ozone tracer simulated with FLEXPART over Garmisch-Partenkirchen captures many details of the evolution of the two observed high-ozone filaments measured with the IFU lidar, thus demonstrating the considerable progress in model simulations. Finally, the modelled ozone (operationally available since October 1999) from the ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric model is shown to be in very good agreement with the observations during this case study, which provides the first successful validation of a chemical tracer that is derived operationally from a weather forecast model. This suggests that coupling chemistry and weather forecast models may significantly improve both weather and chemical forecasts in the future.