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Content archived on 2024-05-24

Precursors of ozone and their effects in the troposphere


Problems to be solved
Tropospheric ozone has a dual role with respect to climatic changes. Ozone is itself a greenhouse gas and it also plays a key role in the production of the hydroxyl radical (OH), which controls the lifetime of many climatically important tropospheric gases. Tropospheric ozone and OH are produced as a result of photochemical processes, through reactions involving ozone precursors.
The proposed project is defined in order to answer three main questions:
first, can the surface emissions of ozone precursors, and their variability be accurately quantified?
Second, how should the current observations of chemical species be optimally coupled with chemistry-transport models (CTMs) to quantify the global budgets of ozone precursors and ozone?
Third, how do future changes in surface emissions and proposed future scenarios influence the lifetime of greenhouse gases and ozone distribution?
The project will provide a quantitative basis for emissions, distributions and evolution of chemical tropospheric species for discussions related to policies aimed at improving the quality of air or at reduction of greenhouse species anthropogenic emissions.
Scientific objectives and approach
The overall objective of the project is to quantify accurately the budget of ozone precursors using a combination of observations and state of the art CTM. The retrieval methods to derive accurately the tropospheric burdens of CO, CH4, NO2 and ozone from observations provided by the IMG/ADEOS and GOME instruments will be improved. High-resolution inventories of emissions for ozone precursors will be developed. The ability of several European CTMs to reproduce current distributions will be assessed, through detailed comparisons between model results and observations. The impact of changes in ozone precursors on the tropospheric oxidising capacity and on the distribution of ozone will be quantified. The relative importance of anthropogenic versus natural emissions in the ozone production will be quantified. The inverse modelling approach for quantifying surface emissions will be further developed. These developments will yield an assessment of the accuracy of current inventories. The impact of emission mitigation policies on the distributions of methane and ozone will be quantified.
Expected impacts
The proposed project addresses issues that are central to our understanding of the causes of large-scale air pollution and climate change, and will provide a quantitative basis for reducing the environmental and climatic impact of human activities. The new tools and databases we will develop will aid the understanding of changes in the composition of the atmosphere and their consequences. The emissions distributions we will optimise could be used as a starting point for discussions on emissions reduction policies. The inverse modelling methodology developed within the project will be available for the optimisation and verification of surface emissions of other chemical species for which measurements will be available in the future. The project will allow a better knowledge of the behaviour of ozone precursors and ozone, and yield a quantitative understanding of the importance of the processes that determine their budgets and their evolution. This represents an important step in reducing uncertainties about the impact of changes in ozone precursors on the concentration of ozone, which is important for policy makers to decide upon efficient options for future mitigation policies. The project will therefore provide an important reference for the evaluation of future global trends using the existing and future satellite observations.

Call for proposal

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EU contribution
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Participants (9)