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Geosciences LibreTexts

10.10: Measuring Winds

  • Page ID
    10201
  • For weather stations at the Earth’s surface, wind direction can be measured with a wind vane mounted on a vertical axle. Fixed vanes and other shapes can be used to measure wind speed, by using strain gauges to measure the minute deformations of the object when the wind hits it.

    The generic name for a wind-speed measuring device is an anemometer. A cup anemometer has conic- or hemispheric-shaped cups mounted on spokes that rotate about a vertical axle. A propeller anemometer has a propeller mounted on a horizontal axle that is attached to a wind vane so it always points into the wind. For these anemometers, the rotation speed of the axle can be calibrated as a wind speed.

    Other ways to measure wind speed include a hotwire or hot-film anemometer, where a fine metal wire is heated electrically, and the power needed to maintain the hot temperature against the cooling effect of the wind is a measure of wind speed. A pitot tube that points into the wind measures the dynamic pressure as the moving air stagnates in a dead-end tube. By comparing this dynamic pressure with the static pressure measured by a different sensor, the pressure difference can be related to wind speed.

    Sonic anemometers send pulses of sound back and forth across a short open path between two opposing transmitters and receivers (transceivers) of sound. The speed of sound depends on both temperature and wind speed, so this sensor can measure both by comparing sound travel times in opposite directions. Tracers such as smoke, humidity fluctuations, or clouds can be tracked photogrammetrically from the ground or from remote sensors such as laser radars (lidars) or satellites, and the wind speed then estimated from the change of position of the tracer between successive images. 

    Measurements of wind vs. height can be made with rawinsonde balloons (using a GPS receiver in the sonde payload to track horizontal drift of the balloons with time), dropsondes (like rawinsondes, only descending by parachute after being dropped from aircraft), pilot balloons (carrying no payload, but being tracked instead from the ground using radar or theodolites), wind profilers, Doppler weather radar (see the Satellites & Radar chapter), and via anemometers mounted on aircraft.