Accueil > Actualités > Séminaires > Séminaire de Benoit Semin


Titre : A model experiment of the quasi-biennial oscillation
Nom du conférencier : Benoit Semin
Son affiliation : ESPCI
Laboratoire organisateur : LMD
Date et heure : 01-02-2018 14h00
Lieu : LMD-ENS - 24 rue Lhomond - 75005 Paris - salle E314
Résumé :

The quasi-biennial oscillation is the periodic reversal of the wind in the lower equatorial stratosphere. The period of the oscillation is 28 months on average, and is not linked to the year duration. This wind is known to be generated by atmospheric waves, in particular internal gravity waves. We have set up an experiment which reproduces this phenomenon. Linearly stratified salty water is located between two plexiglas cylinders. Internal gravity waves are generated in the fluid using 16 membranes located at the top of the fluid. Each membrane oscillates sinusoidally in the vertical direction, in opposition of phase with its two neighbors: the wave is stationary in the azimuthal direction. When the amplitude of the forcing is large enough, a mean flow is generated, and oscillates with a period which is much larger than the wave period. This oscillation of the mean flow is similar to the one observed in the atmosphere. We have shown that the bifurcation can be either sub-critical or super-critical, depending on the parameters.

Contact :