Meteorological towers (met towers) are
the most common means for measuring the wind speed and direction at
a site. A met tower is a tall, tubular steel tower generally 40 m
or 50 m tall, with tower diameters of approximately 6-8 inches.
These towers are secured via four sets of guy wires, which connect
from the tower at several heights to four sets of anchors on the
ground. The wind speed and direction are measured using anemometers
for the wind speed, and wind vanes for the direction. These sensors
are usually positioned at two or three heights on the tower, with
two anemometers at each height, and one vane. At each height,
approximately six-foot long booms are attached to the tower
extending horizontally. The wind monitoring sensors are secured to
the end of the booms. Thus, there are usually three booms at each
height, and the booms for the anemometers are positioned in
opposite directions. By positioning the sensors away from the
tower, the effects of the tower wake are reduced. The sensors
usually produce data that gives the average wind speed and wind
direction over 10-minute intervals. These data are recorded and
stored by a logger box at the bottom of the tower, which is
connected to the sensors via sensor cable.