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Contribution des échauffements stratosphériques à la variabilité et à l'évolution à long terme de la moyenne atmosphère : observations et modélisations numériques

Guillaume Angot 1
1 STRATO - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The influence of stratospheric conditions on the climate has recently become widely accepted. Coupling in the stratosphere-troposphere system causes large amplitude dynamical activity occurring in the middle atmosphere to have significant consequences on the troposphere's equilibrium and flow. Sudden stratospheric warmings are the clearest and strongest manifestation of such activity. This study focuses on the impact of these events on the variability of the middle atmosphere and on estimations of temperature trends. Another objective of our work is to acquire a better understanding of the evolution of a stratospheric warming, from the state of the atmosphere that initiates such an event to its consequences on both the middle atmosphere and the troposphere from a few days to a couple of months after it. First, we describe a novel methodology to perform a statistical analysis of long series and we apply it on a lidar measurement from the Haute-Provence Observatory. The large dynamical activity and the so-called background component can be distinguished, which allows to explain the differences observed between summer and winter. Second, the methodology is validated and its results are extended to a global scope thanks to a dataset from the Canadian Middle Atmosphere Model. Spatial differences are also explained by variations in the dynamical activity. Third, sensitivity tests are performed using RACCORD model to investigate what state of the atmosphere leads to a major stratospheric warming. Meteorological nudging is essential to produce a major warming, especially for split-type events. Last, our results are applied and compared to a case-study of winter 2012-2013.
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  • HAL Id : tel-01056057, version 1

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Guillaume Angot. Contribution des échauffements stratosphériques à la variabilité et à l'évolution à long terme de la moyenne atmosphère : observations et modélisations numériques. Sciences de l'environnement. Université Pierre et Marie Curie - Paris VI, 2013. Français. ⟨tel-01056057⟩

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