Wind field modifications due to an anemometer tower

Variations in wind velocity and direction due to the mounting structure are studied using Gill anemometers mounted on 1.8 m long arms of a 232 m high tower. The tower «shadowing» effect for the observed range, from 0 to 20 m/s, is in linear correlation with the velocity. The polar diagrams of the variations in wind speed and direction are presented as a function of the wind's direction. The horizontal component decreases by 15% when the anemometer is on the windward side of the tower, and by a maximum of 80% on the lee side. In the latter case the decrease is highly sensitive to wind direction. Variations in direction do not exceed 15 degrees.