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| Galani E., D. Balis, P. Zanis, C. Zerefos, A. Papayannis, H. Wernli and E. Gerasopoulos | [abstract]
In order to cover a substantial amount of stratospheric intrusions during the project
Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric
Transport and Oxidation Capacity (STACCATO), coordinated measurements were carried
out at several locations in central and southern Europe, based on quasi-operational
stratosphere-troposphere exchange forecasts. In this context, lidar measurements of
tropospheric ozone were performed at Thessaloniki (23_E, 40.5_N), Greece, for the
investigation of stratosphere-to-troposphere transport (STT) events over the southeastern
Mediterranean region, during 2000-2002. The study of STT in this area is of particular
interest not only because of its geographic location, which is more southern than the
typical position of the polar front jet, but also because of the sparseness of detailed studies in
this area.Asummary of the main characteristics of the STTevents that were detected by lidar
during the investigation period reveals a tropospheric ozone increase of the order of 10%
between 4.5 and 6.5 km above sea level, a coincident decrease in relative humidity, and
elevated values of potential vorticity, thus providing a direct indication of the occurrence of
stratospheric air in the middle troposphere. No direct effect on surface ozone was recorded.
Furthermore, the majority of the STT cases detected reveal a common pathway of the
stratospheric air masses that reached Thessaloniki originating from the North Sea. In
addition, the event of 9 January 2001, during which the clearest and strongest descent
of stratospheric air occurred, is further analyzed. An ozone-rich layer of the order of
60-90 ppbv between 5 and 6.5 km above sea level is clearly depicted, which was the
result of the intermixture of originally stratospheric and boundary layer air originating
from North America. | [keywords]
Stratosphere, troposphere, lidar | | J. of Geophys. Res., 2002 | | |  back to publications list |
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