Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 14025-14039, 2016
http://www.atmos-chem-phys.net/16/14025/2016/
doi:10.5194/acp-16-14025-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
11 Nov 2016
On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East
Dimitris Akritidis1,2, Andrea Pozzer1, Prodromos Zanis2, Evangelos Tyrlis3, Bojan Škerlak4, Michael Sprenger4, and Jos Lelieveld1,3 1Max Planck Institute for Chemistry, Mainz, Germany
2Department of Meteorology and Climatology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece
3Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia, Cyprus
4Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Abstract. We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

Citation: Akritidis, D., Pozzer, A., Zanis, P., Tyrlis, E., Škerlak, B., Sprenger, M., and Lelieveld, J.: On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East, Atmos. Chem. Phys., 16, 14025-14039, doi:10.5194/acp-16-14025-2016, 2016.
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We investigate the contribution of tropopause folds in the summertime tropospheric ozone pool over the eastern Mediterranean and the Middle East. For this purpose we use the EMAC atmospheric chemistry–climate model and a fold identification algorithm. A clear increase of ozone is found in the middle troposphere due to fold activity. The interannual variability of near-surface ozone over the eastern Mediterranean is related to that of both tropopause folds and ozone in the free troposphere.
We investigate the contribution of tropopause folds in the summertime tropospheric ozone pool...
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