Vertical variation of frequency distributions of wind speed in and above the surface layer observed by sodar

10 min-averaged wind speed data have been measured with a mini-sodar for 13 months subsequently at different sites in level terrain and on hill tops i n Germany in the last three years. The data presented here is from a height range between 25 and 140 m above ground, the vertical resolution is 5 to 1 0 m. From the data monthly mean diurnal courses of wind speed and of direct ional shear have been computed as well as monthly mean vertical profiles of the scale factor and the shape parameter of the WEIBULL wind speed frequen cy distribution. These profiles extend beyond the top of the surface layer into the EKMAN layer. Therefore the profiles have to be described by EKMAN layer laws instead of by surface layer laws if they have to be extrapolated upward. Typical features of the profiles characterizing level terrain and hill top sites have been analyzed. Most prominent feature is the maximum of the shape parameter at the top of the surface layer. Implications for the siting of wind turbines are discussed.