Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Vertical ozone transports in the Alps (VOTALP)

The European Union (EU) research project VOTALP, carried out between March 1996 and February 1998, investigated transport and formation of ozone in the Alps, focusing on processes which can cause increased ozone concentrations, namely stratospheric intrusions, horizontal advection of polluted air masses, and in-situ production of ozone due to local emissions in Alpine valleys. Stratospheric intrusions were identified at mountain peak observatories and in the free troposphere above the Alps. Time-series analyses and single case studies revealed an occurrence of direct intrusions during approximately 5-10% of the time, making a contribution to the monthly averaged ozone concentrations at peak level (2500-4000 m) of approximately 2-5 parts per billion (ppb). Foundations have been laid for the derivation of climatological estimates of stratospheric intrusions in the follow-up project VOTALP II. Horizontal advection of ozone by local-scale and large-scale wind systems was found to be highly relevant for the Alpine region, leading to high ozone concentrations observed in Alpine valleys as well as at elevated sites. A climatological assessment showed that nearby emission areas such as the Po Valley and Southern Germany are especially important for the air quality in the Alps. As far as local in-situ production of ozone in Alpine valleys is concerned, case studies revealed that, despite of substantial photochemical ozone production, no corresponding increase of ozone concentration within the valley was observed. The ozone production is probably balanced by efficient destruction processes like dry deposition. Simplified measurement-based budget calculations showed that valleys might be very efficient in pumping boundary layer air into the 'free' troposphere aloft. In the Mesolcina Valley, a volume of air equal to three to six times the valley volume is ejected into the 'free' troposphere during one up-valley wind phase.

Reported by

Universität für Bodenkultur Wien
Türkenschanzstrasse 18
1180 Wien
Austria
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