Evaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations C. Vigouroux1, M. De Mazière1, P. Demoulin2, C. Servais2, F. Hase3, T. Blumenstock3, I. Kramer3, M. Schneider3, J. Mellqvist4, A. Strandberg4, V. Velazco5, J. Notholt5, R. Sussmann6, W. Stremme6, A. Rockmann6, T. Gardiner7, M. Coleman7, and P. Woods7 1Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium 2Institut d'Astrophysique et de Géophysique, University of Liège (ULg), Liège, Belgium 3Institute for Meteorology and Climate Research (IMK-ASF), Forschungszentrum Karlsruhe and University of Karlsruhe, Karlsruhe, Germany 4Chalmers University of Technology, Göteborg, Sweden 5Institute of Environmental Physics, University of Bremen, Bremen, Germany 6Institute for Meteorology and Climate Research (IMK-IFU), Forschungszentrum Karlsruhe, Garmisch-Partenkirchen, Germany 7National Physical Laboratory, Teddington, UK
Abstract. Within the European project UFTIR (Time series of Upper Free Troposphere observations from
an European ground-based FTIR network), six ground-based stations in Western Europe, from
79° N to 28° N, all equipped with Fourier Transform infrared (FTIR)
instruments and part of the Network for the Detection of Atmospheric Composition Change
(NDACC), have joined their efforts to evaluate the trends of several direct and indirect
greenhouse gases over the period 1995–2004. The retrievals of CO, CH4, C2H6, N2O,
CHClF2, and O3 have been optimized. Using the optimal estimation method, some vertical
information can be obtained in addition to total column amounts. A bootstrap resampling method
has been implemented to determine annual partial and total column trends for the target gases.
The present work focuses on the ozone results. The retrieved time series of partial and total
ozone columns are validated with ground-based correlative data (Brewer, Dobson, UV-Vis, ozonesondes,
and Lidar). The observed total column ozone trends are in agreement with previous studies: 1) no total
column ozone trend is seen at the lowest latitude station Izaña (28° N); 2) slightly
positive total column trends are seen at the two mid-latitude stations Zugspitze and Jungfraujoch
(47° N), only one of them being significant; 3) the highest latitude stations Harestua
(60° N), Kiruna (68° N) and Ny-Ålesund (79° N) show significant positive total column trends.
Following the vertical information contained in the ozone FTIR retrievals, we provide partial
columns trends for the layers: ground-10 km, 10–18 km, 18–27 km, and 27–42 km, which helps
to distinguish the contributions from dynamical and chemical changes on the total column ozone trends.
We obtain no statistically significant trends in the ground-10 km layer for five out of the six
ground-based stations. We find significant positive trends for the lowermost stratosphere at the two
mid-latitude stations, and at Ny-Ålesund. We find smaller, but significant trends for the 18–27 km
layer at Kiruna, Harestua, Jungfraujoch, and Izaña. The results for the upper layer are quite contrasted:
we find significant positive trends at Kiruna, Harestua, and Jungfraujoch, and significant negative trends
at Zugspitze and Izaña. These ozone partial columns trends are discussed and compared with previous studies.
Citation: Vigouroux, C., De Mazière, M., Demoulin, P., Servais, C., Hase, F., Blumenstock, T., Kramer, I., Schneider, M., Mellqvist, J., Strandberg, A., Velazco, V., Notholt, J., Sussmann, R., Stremme, W., Rockmann, A., Gardiner, T., Coleman, M., and Woods, P.: Evaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations, Atmos. Chem. Phys., 8, 6865-6886, doi:10.5194/acp-8-6865-2008, 2008.