Caractérisation de la pollution dans la troposphère arctique : utilisation des données satellitaires et aéroportées dans le cadre de la campagne API/POLARCAT

Matthieu Pommier 1
1 TROPO - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The Arctic is a region which despite the remoteness and lack of emission sources of pollutants, is one of the most affected by the long-range transport of pollution, which can affect background pollution levels and which influence climate change both regionally and globally. Despite improvements in observing systems and numerical models in recent decades, it remains difficult to reproduce the observed pollution episodes in the Arctic especially in summertime. One possible explanation is the underestimation of modelled ozone (O3) production in forest fires plumes. Carbon monoxide (CO) is often used as a tracer of pollution transport due to its relatively long lifetime of several weeks in the troposphere. It is a reactive gas, mainly produced by the combustion of fossil fuels and vegetation burning. Moreover, since its main sink is reaction with OH radical, CO has an important role in the oxidizing power of the atmosphere it also plays an important role in the assessment of tropospheric ozone. The purpose of my thesis has been to contribute to a better understanding of transport and of the chemical mechanisms of pollutants formation in the Arctic troposphere. A combination of the new CO measurements from the IASI satellite instrument, launched in October 2006 aboard the MetOp-A and aircraft data collected during the POLARCAT campaigns of the International Polar Year (IPY), in spring and summer 2008 were used. IASI CO observations were first validated by comparison with in situ airborne measurements showing its ability to detect the evolution of high CO signatures plume as close to sources regions. The second part of the thesis used assimilation of daily IASI CO measurements (Kalman filter) in the LMDz-INCA global model to improve our understanding about sources of pollution impacting the Arctic troposphere and their transport pathways. The assimilation has improved the modelling of CO pollution episodes in the Arctic free troposphere. Model results were also evaluated using POLARCAT observations and used to examine the sensitivity of Arctic pollutant concentrations (namely the overestimation of O3 distribution and the underestimation of PAN distribution) to emissions from different regions and in particular the boreal forest fire emissions.
Document type :
Theses
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Submitted on : Wednesday, April 20, 2011 - 8:02:11 PM
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Matthieu Pommier. Caractérisation de la pollution dans la troposphère arctique : utilisation des données satellitaires et aéroportées dans le cadre de la campagne API/POLARCAT. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00587583⟩

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