SODAR WIND-SPEED PROFILES OVER FORESTED BOUNDARY-LAYER DURING THE HAPEX-MOBILHY CAMPAIGN

Sodar and minisodar wind speed profiles above two different canopies (forested and clearing site) are analysed in terms of a logarithmic law. The friction velocities and roughness lengths derived from acoustic sounding data are compared with those derived from radiosounding data or measured by the hydra system. During periods of neutral or quasi neutral atmospheric stability conditions, the friction velocity estimations are in good agreement whatever the method of measurement (aerodynamic or correlation), the data type (space and time resolution), the parameterization used, or the site area. All these factors slightly influence the friction velocity and we are able to determine their combined effects. The whole minisodar data set has been analysed. Below 60 m the logarithmic law fits the wind profile whatever the atmospheric stability conditions are. The friction velocities deduced from minisodar data are in good agreement with the hydra friction velocities, with an error bar of 20%.