One year ozonesonde measurements at Kerguelen Island (49.2°S, 70.1°E): Influence of stratosphere-to-troposphere exchange and long-range transport of biomass burning plumes

Authors

  • Jean-Luc Baray,

    1. Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, Centre National de la Recherche Scientifique, Météo-France, Université de la Réunion, La Réunion, France
    2. Unité Mixte de Service de l'OSU Réunion, UMS 3365, Centre National de la Recherche Scientifique, Université de la Réunion, La Réunion, France
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  • Valentin Duflot,

    1. Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, Centre National de la Recherche Scientifique, Météo-France, Université de la Réunion, La Réunion, France
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  • Françoise Posny,

    1. Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, Centre National de la Recherche Scientifique, Météo-France, Université de la Réunion, La Réunion, France
    2. Unité Mixte de Service de l'OSU Réunion, UMS 3365, Centre National de la Recherche Scientifique, Université de la Réunion, La Réunion, France
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  • Jean-Pierre Cammas,

    1. Laboratoire d'Aérologie, UMR 5560, Centre National de la Recherche Scientifique, Université de Toulouse, Toulouse, France
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  • Anne M. Thompson,

    1. Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, USA
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  • Franck Gabarrot,

    1. Unité Mixte de Service de l'OSU Réunion, UMS 3365, Centre National de la Recherche Scientifique, Université de la Réunion, La Réunion, France
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  • Jean-Louis Bonne,

    1. Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, Centre National de la Recherche Scientifique, Météo-France, Université de la Réunion, La Réunion, France
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  • Guang Zeng

    1. National Institute of Water and Atmospheric Research, Lauder, New Zealand
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Abstract

[1] We analyze a 1 year campaign of 17 ozonesondes launched in 2008–2009 at Kerguelen Island (49.2°S, 70.1°E), the first such soundings performed at this location. Tropospheric ozone presents a large variability in austral summer (December to February) and austral winter (June to September). The baseline tropospheric ozone is higher in winter (between 30 and 50 ppbv) than in summer (between 20 and 40 ppbv). We compare these observations to a data set obtained during the same period at Lauder (45.0°S, 169.7°E), which presents a marked seasonal pattern. The analysis of trajectory runs and reanalysis output help identify two significant contributors to the tropospheric ozone level at Kerguelen: the stratosphere-to-troposphere air mass transport and the long-range transport of biomass burning plumes. The stratosphere-to-troposphere transport is exemplified by a case study of a dry and enriched ozone layer over Kerguelen (70 ppbv at an altitude of 6 km on 28 February 2009). Using Lagrangian model simulations, we show that wintertime enhancement of the tropospheric ozone baseline can be partially attributed to the long-range transport of ozone precursors from biomass burning plumes originating in southern America and Africa. However, owing to limited data and to the many factors that can cause this wintertime baseline ozone enhancement, further investigations are needed to fully explain it. Additional measurements are also needed to establish an ozone climatology, to further characterize the ozone annual cycle and wintertime enhancement, and to better compare Kerguelen with other midlatitude sites.

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