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Accueil > Actualités > Séminaires > Séminaires 2018

Mardi 27 mars 2018 à 14h00 en amphi K118

Gabriele Arduini, chercheur au centre européen de recherche pour les prévisions du temps à moyenne échelle (ECMWF), Reading, Angleterre

Titre/Title : Wintertime Stable Boundary-Layer Processes in Alpine Valleys

Contact : Chantal Staquet (Equipe MEIGE)

Résumé/Abstract : Alpine valleys are rarely closed systems, implying that the atmospheric boundary layer (i.e. the part of the atmosphere directly influenced by the presence of the surface) of a particular valley section is influenced by the surrounding terrain and large-scale flows. A detailed characterisation and quantification of these effects is required in order to design appropriate parameterisation schemes for complex terrains. The focus of this thesis is to improve the understanding of the effects of surrounding terrain (plains, valleys or tributaries) and weak large-scale winds on the heat and mass budgets of the stable boundary layer of a valley section, under dry conditions. Numerical simulations using idealised and real frameworks are performed to meet this goal.

Idealised simulations show that the dynamical and 
thermodynamical properties of the nocturnal boundary layer of a valley section are very sensitive to the valley width of an adjacent valley or of a plain nearby. 
Particular emphasis is put on the analysis of transport of heat across the different valley sections.

A case-study of a persistent cold-air pool event in a deep Alpine valley allowed to quantify the effects of neighbouring valleys on the heat and mass budgets of a real valley atmosphere. Tributary flows had significant impact on the height of the inversion layer and the strength of the cold-air pool, transporting a significant amount of warm air within the valley atmosphere throughout the night. The effect of the large-scale flow was found non negligible, impacting the near-surface circulation of the valley.