Wind Turning in The Atmospheric Boundary Layer

Measurements at Hövsöre site in Denmark are used to analyse the change with height of wind speed and the turning of the wind in the atmospheric boundary layer. The purpose is to study the behaviour of wind turning and wind shear and analyse the relations between them. The study will show the effect of wide range of stability classes on the turning of wind and wind speed by combining cup, wind vane and sonic at meteorological mast with lidar observations. Easterly wind is investigated at Hövsöre site to study the behaviour of the overland wind shear and wind turning from November 2008 to April 2009. In this study, data are analysed based on average 10-min wind speeds and wind directions diurnal, monthly and during the whole period of measurements. The results show that first, the wind speed profile of meteorological mast and lidar are in agreement to different stability classes. Second, the wind direction profile changes with height reasonable in all stability conditions except in very unstable and unstable cases. Third result shows that the wind shear and the wind turning are unstable during the day and stable during the night in the average whole period of six months. Fourth, the yearly wind turning and wind shear are in agreement without considering lidar observations. They behave also in similar way when lidar observations combine with meteorological mast. In conclusion, the comparisons between the wind shear and the turning of the wind with and without considering lidar observation show that the wind shear is in the agreement with the wind turning. The second result on this study was unexpected. The reason for this behaviour may be explained as the number of measurements are very low. Another reason is that the value of heat fluxes are low, whereas they have to be high. The last reason might be related to a baroclinicity