Errors in Wind Measurements Associated with Tower-Mounted Anemometers1

Abstract

Towers distort the wind flow and thereby may produce errors in wind speed and direction measurements obtained by anemometers mounted on them. To study this effect, a comparison was made of 5000 hourly wind observations obtained from each of two Aerovanes operating simultaneously. One was mounted on a lattice-type tower and the other was mounted on a utility pole free from the tower wind-shadow effect. Both instruments were located at the meteorological field site of the Argonne National Laboratory. The results show that there was a substantial reduction in the wind speed indicated by the tower-mounted anemometer when the wind passed through the tower before being measured. For some wind directions, the tower-mounted anemometer gave speed readings appreciably higher than those of the reference anemometer. Wind-direction measurements were also affected. The data indicate that for precise work the tower wind-shadow effect must be considered.