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Accueil > Actualités > Séminaires > Séminaires 2009

Mardi 15 décembre à 11h00 - amphi Craya

Maria Antonia Jiménez Cortes (Groupe de Météorologie, Université des Iles Baléares, Espagne)

Titre/Title :
THE ORGANIZATION OF THE FLOW IN A BASIN

Contact :
Christophe Brun

Résumé/Abstract :
The organization of the flow during night-time and clear-sky conditions in
the Duero basin is analyzed using observations (AWS, 100 m tower and
satellite images) and high-resolution mesoscale simulations. As night advances, the surface temperature cools down, specially in the center of a basin, and the air flows along the mountain slopes and tend to concentrate in the center of the basin. The locally generated effects favor the formation of a wind maxima (Low-Level Jet, LLJ) at about 100 m above the ground level, which usually coincides with the height where the temperature gradient changes. The available observations seem to confirm these modeled findings. Furthermore, data from satellite images show
that large basins with relatively wide and flat floors experience heterogeneous nocturnal cooling due to the diversity of the topography and the land use.

The physical mechanisms that take place in an observed LLJ in the basin
are also analyzed using Large-Eddy Simulations (LES). The LES results show that the level of the wind maximum, usually coincident with a change of the temperature gradient, acts as a decoupling layer where the transport across it is very small and intermittent.