Processes influencing ozone levels in Alaskan forest fire plumes during long-range transport over the North Atlantic

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Real, Elsa, Law, Kathy S., Weinzierl, Bernadett, Fiebig, M., Petzold, A., Wild, O., Methven, J., Arnold, S., Stohl, A., Huntrieser, H., Roiger, Anke, Schlager, H., Stewart, D., Avery, M., Sachse, G., Browell, E., Ferrare, R., Blake, D.
• Other Authors: Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), DLR Institut für Physik der Atmosphäre (IPA), Deutsches Zentrum für Luft- und Raumfahrt Oberpfaffenhofen-Wessling (DLR), Centre for Atmospheric Science Cambridge, UK, University of Cambridge UK (CAM), Department of Meteorology Reading, University of Reading (UOR), School of Earth and Environment Leeds (SEE), University of Leeds, Norwegian Institute for Air Research (NILU), School of Environmental Sciences Norwich, University of East Anglia Norwich (UEA), NASA Langley Research Center Hampton (LaRC), Department of Chemistry Irvine, University of California Irvine (UCI), University of California-University of California, INSU-CNRS, ADEME, Institut Pierre Simon Laplace (IPSL), Institut Geographique National (IGN)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: photochemistry; long-range transport; boreal fires; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; North Atlantic; Alaska
• Online Access: https://hal.archives-ouvertes.fr/hal-00164294; https://hal.archives-ouvertes.fr/hal-00164294/document; https://hal.archives-ouvertes.fr/hal-00164294/file/Real_et_al-2007-Journal_of_Geophysical_Research__Atmospheres_%281984-2012%29.pdf; https://doi.org/10.1029/2006JD007576

A case of long-range transport of a biomass burning plume from Alaska to Europe is analyzed using a Lagrangian approach. This plume was sampled several times in the free troposphere over North America, the North Atlantic and Europe by three different aircraft during the IGAC Lagrangian 2K4 experiment which was part of the ICARTT/ITOP measurement intensive in summer 2004. Measurements in the plume showed enhanced values of CO, VOCs and NO y , mainly in form of PAN. Observed O 3 levels increased by 17 ppbv over 5 days. A photochemical trajectory model, CiTTyCAT, was used to examine processes responsible for the chemical evolution of the plume. The model was initialized with upwind data and compared with downwind measurements. The influence of high aerosol loading on photolysis rates in the plume was investigated using in situ aerosol measurements in the plume and lidar retrievals of optical depth as input into a photolysis code (Fast-J), run in the model. Significant impacts on photochemistry are found with a decrease of 18% in O 3 production and 24% in O 3 destruction over 5 days when including aerosols. The plume is found to be chemically active with large O 3 increases attributed primarily to PAN decomposition during descent of the plume toward Europe. The predicted O 3 changes are very dependent on temperature changes during transport and also on water vapor levels in the lower troposphere which can lead to O 3 destruction. Simulation of mixing/dilution was necessary to reproduce observed pollutant levels in the plume. Mixing was simulated using background concentrations from measurements in air masses in close proximity to the plume, and mixing timescales (averaging 6.25 days) were derived from CO changes. Observed and simulated O 3 /CO correlations in the plume were also compared in order to evaluate the photochemistry in the model. Observed slopes change from negative to positive over 5 days. This change, which can be attributed largely to photochemistry, is well reproduced by multiple model runs even if ...