Simulation aux grandes échelles de traînées de condensation dans un milieu atmosphérique stratifié et turbulent.

Abstract : Modeling the effects of contrails into large-scale models requires accurate parametrisations of their characteristics. However, measures of contrails are too rare and not exhaustive to well define and validate these parametrisations. Detailed simulations of contrails allow the analysis of their physics, leading to improved measurement and more accurate parametrisations. Studies of aircraft wakes have shown the importance of atmospheric turbulence in the dynamics of wake vortices. Nevertheless, in most of contrail simulations performed so far, turbulence was not sustained and not explicitly resolved. In this thesis, we set up a simulation strategy for contrails that uses a three dimensional description of wake dynamics and turbulence. Firstly, a stochastic forcing method is setup to generate turbulent flows in a stratified medium, and we show that this method is able to mimic atmospheric turbulence. Secondly, contrail simulations embedded in this turbulence field are performed. Effects of turbulence, temperature and water vapour saturation are studied: turbulence controls the break-up of wake vortices, while saturation and temperature control deposition rate of water vapour on ice crystals and their persistence in the long term. Computed microphysical and optical properties are in agreement with observations and ad-hoc relations are proposed to incorporate theses properties into contrail parametrisations for large-scale models.
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Submitted on : Friday, May 31, 2013 - 10:41:28 AM
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Joris Picot. Simulation aux grandes échelles de traînées de condensation dans un milieu atmosphérique stratifié et turbulent.. Océan, Atmosphère. Université de Toulouse III - Paul Sabatier, 2013. Français. ⟨tel-00828483⟩

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