Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 4 2005 10.5194/acpd-5-7247-2005 http://www.atmos-chem-phys-discuss.net/5/7247/2005/ http://www.atmos-chem-phys-discuss.net/5/7247/2005/acpd-5-7247-2005.html http://www.atmos-chem-phys-discuss.net/5/7247/2005/acpd-5-7247-2005.pdf 7247 7282 2005-08-22 Seasonal cycles and variability of O3 and H2O in the UT/LMS during SPURT M. Krebsbach C. Schiller D. Brunner G. Günther M. I. Hegglin D. Mottaghy M. Riese N. Spelten H. Wernli Institute for Chemistry and Dynamics of the Geosphere: Stratosphere, Research Centre Jülich GmbH, Jülich, Germany Institute for Atmospheric and Climate Science, Federal Institute of Technology, Zurich, Switzerland Applied Geophysics, RWTH Aachen University, Aachen, Germany Institute for Atmospheric Physics, University of Mainz, Mainz, Germany Airborne high resolution in situ measurements of a large set of trace gases including ozone (O3) and total water (H2O) in the upper troposphere and the lowermost stratosphere (UT/LMS) have been performed above Europe within the SPURT project. With its innovative campaign concept, SPURT provides an extensive data coverage of the UT/LMS in each season within the time period between November 2001 and July 2003. Ozone volume mixing ratios in the LMS show a distinct spring maximum and autumn minimum, whereas the O3 seasonal cycle in the UT is shifted by 2 to 3 month later towards the end of the year. The more variable H2O measurements reveal a maximum during spring/summer and a minimum during autumn/winter with no phase shift between the two atmospheric compartments. For a comprehensive insight into trace gas composition and variability in the UT/LMS several statistical methods are applied using chemical, thermal and dynamical vertical coordinates. In particular, 2-dimensional probability distribution functions serve as a tool to transform localised aircraft data to a more comprehensive view of the probed atmospheric region. It appears that both trace gases, O3 and H2O, reveal the most compact arrangement and are best correlated in the view of potential vorticity (PV) and distance to the local tropopause, indicating an advanced mixing state on these surfaces. Thus, strong gradients of PV seem to act as a transport barrier both in the vertical and the horizontal direction. The alignment of trace gas isopleths reflects the existence of a year-round extra-tropical tropopause transition layer. The SPURT measurements reveal that this layer is mainly affected by stratospheric air during winter/spring and by tropospheric air during autumn/summer. Mixing entropy values for O3 and H2O in the LMS appear to be maximal during spring and summer, respectively, indicating highest variability of these trace gases during the respective seasons.