anemometry

Anemometry is the branch of metrology concerned with measuring wind speed and, in some cases, wind direction. It encompasses instruments and methods for quantifying the velocity of air in the atmosphere. In meteorology and engineering, anemometers provide data on mean wind speed, instantaneous velocity, and turbulence characteristics, essential for weather forecasting, climate studies, wind-energy assessment, and HVAC design.

Mechanical anemometers include cup-and-rotor devices that infer wind speed from rotation, and vane or propeller types that also indicate direction. Thermal anemometers use heated sensors whose cooling rate varies with air velocity. Ultrasonic and laser-based instruments determine wind from time-of-flight or Doppler shifts and provide fast, three-dimensional sensing. Pitot tubes measure dynamic and static pressure to infer airspeed, widely used in aviation and wind tunnels.

Measurement practice emphasizes siting, height above ground, and exposure to obstacles, as wind speed depends on roughness and stability. Standard meteorological practice often uses 2 to 10 meters above ground, with averaging over intervals such as 1 to 10 minutes and reporting of gust factors and turbulence intensity.

Calibration occurs in wind tunnels or against traceable references; instruments require regular maintenance, temperature compensation for some sensors, and care against icing or fouling. Response time and geometry can bias fast fluctuations; ultrasonic sensors can be sensitive to temperature and humidity and require corrections.

Anemometry supports weather forecasting, climate research, wind-energy resource assessment, building ventilation design, and aviation safety. In research, advanced techniques such as laser Doppler anemometry and particle image velocimetry provide high-resolution velocity fields in controlled flows.