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Maximum oxidation rates in the free troposphere


There are still severe limits to our understanding of processes which control tropospheric ozone and the oxidation capacity of the atmosphere and hence also the air quality at the earth's surface. The aim of this proposal is to employ a well integrated combination of airborne measurements with state-of-the art statistical and deterministic models to address some of the uncertainties related to resolving the relationship between pollutant emissions and the concentration distribution of ozone and other species related to the oxidation capacity of the atmosphere.
The main objective of the project is to investigate how the annual cycle of ozone in the troposphere is influenced by atmospheric pollution on a continental and hemispheric scale from the surface and up to the upper troposphere. Specifically, it will be investigated if there
is a chemical cause for the spring/summertime ozone maximum in background air over Europe and the North Atlantic. It will be investigated if there is major ozone destruction in the free troposphere in summer outside of the polluted layers which are often found throughout the troposphere over the North Atlantic. The concentration contrasts in ozone, precursors and intermediate species including free radicals, between the atmospheric boundary layer and the free troposphere will be measured over the European continent, including the Iberian Peninsula, and over the adjacent ocean. The data will be applied to assess the strength of the exchange of pollution between the atmospheric boundary layer and the free troposphere starting in February and continuing until July. It will furthermore be investigated if comprehensive chemical measurements in the atmospheric boundary layer and the free troposphere can show that a concentration range exists for oxides of nitrogen where the oxidation rates of precursors have maxima, as indicated by theoretical calculations, and also, where there is a shift from net photochemical production of ozone to net photochemical destruction.
The project is centred around measurements from the Meteorological Research Flight C- 130 aircraft with a range of 5000 km and a ceiling of 10 km equipped with very extensive and advanced instrumentation for a complete set of measurement of chemical precursors, photooxidants and intermediate products including radical species.
The measurements will allow the calculation of the hydroxyl radical concentration and the net chemical formation rate of ozone in near real time, allowing a very detailed mapping of their variability in space and with time. Measurements will be carried out in late winter, during spring and early summer in a range of weather situations outside of major cloud systems, with vertical profiles from the ground to the upper troposphere in combination with horizontal trancepts in the free troposphere over Europe including the Iberian Peninsula and over the North Atlantic. In support of the aircraft measurements and to address the scientific questions in the project, 3-dimensional numerical models will be used including an advanced state of the art three-dimensional coupled numerical weather prediction-chemistry model. Algorithms and statistical relationships will be employed to screen the measured results and derive preliminary answers to the scientific questions related to the objectives of the project. Later the numerical models will be applied to assimilate the measured results into the model calculations in order to enhance the diagnostic as well as predictive capability of the models.
In this way their reliability as tools for assessing the consequences for air quality of planned abatement measures will be enhanced. The project therefore will contribute significantly to the combat of air pollution. The instrumentation and the methodology for interpretation draw heavily on the development, investment and experience in previous projects funded by the Commission and by other international and national research agencies (OCTA, TACIA and others) and the concortium includes six well-known partners in four European countries.

Call for proposal

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Instituttveien 18
2027 Kjeller

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EU contribution
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Participants (5)