étude expérimentale de la couche limite au-dessus d'un relief modéré proche d'une chaîne de montagne |
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| Authors: | A Druilhet J Noilhan B Benech G Dubosclard D Guedalia J Frangi |
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| Institution: | (1) Laboratoire de Physique des Aérosols et Echanges Atmosphériques, Université Paul Sabatier, 31000 Toulouse, France;(2) Centre de Recherches Atmosphériques, I.O.P.G. du Puy de Dôme, 65300 Lannemezan, France;(3) Institut et Observatoire de Physique du Globe du Puy de Dôme, 63000 Clermont Ferrand, France |
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| Abstract: | For the heterogeneous site described in the first part, some aspects of the turbulent structure of the planetary boundary layer are studied. Using mixed-layer scaling, the normalized profiles are compared with those obtained over flat terrain during convective conditions. The measurements were made with the same instrumented aircraft at both sites. The dissipative and spectral length scales are smaller over complex terrain within the whole boundary layer. This is due to the shifting of the wavelength peak toward the high frequencies by dynamic turbulence.This last effect can also explain the increase of the dissipation rate  over the heterogeneous site during strong wind conditions. The vertical profiles of sensible heat flux and temperature-water vapor correlation show a lack of entrainment process at the top of the boundary layer. This fact suggests that the investigated boundary layer is advected from the neighbouring plain over the complex site (plateau de Lannemezan). |
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