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étude expérimentale de la couche limite au-dessus d'un relief modéré proche d'une chaîne de montagne |
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| Authors: | G Dubosclard B Benech J Noilhan A Druilhet |
| Institution: | 1. Institut et Observatoire de Physique du Globe du Puy de D?me, 63000, Clermont Ferrand, France 2. Centre de Recherches Atmosphériques, I.O.P.G. du Puyde D?me, 65300, Lannemezan, France 3. Laboratoire de Physique des Aérosols et Echanges Atmosphériques Université Paul Sabatier, 31000, Toulouse, France |
| Abstract: | Doppler sodar derived values of the temperature structure parameter C infT sup2 , the vertical velocity variance ¯′w 2, and the rate of dissipation of turbulent energy ?, were measured during unstable conditions above the Lannemezan heterogeneous site. The vertical profiles of these turbulent parameters, normalized by the classical convective scales are compared with those obtained using the same acoustic sounder above an homogeneous site during convective conditions. The typical decrease of C infT sup2 as Z -4/3 is partially verified on the heterogeneous site: for the lower levels, C infT sup2 exhibits an increase with Z whereas for the intermediate levels C infT sup2 . decreases as Z -4/3. For the upper levels, C infT sup2 increases with Z due to a signal-to-noise ratio lower than 1. The vertical profiles of ¯′w 2 above the two sites are rather similar. However, near the base of the convective inversion Z i , the values measured on the heterogeneous site are more scattered. The same scattering is also observed with the ? values; moreover, for the lower levels (Z<0.17Z i ) the increase of ? as Z decreases is more important at the homogeneous site than at the heterogeneous one. It is suggested that these particular features observed at lower levels above the heterogeneous site are mainly related to a complex local boundary layer induced by the near environment of the sodar (vegetation and relief). |
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