In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer.
An anemometer is commonly used to measure wind speed.
The original anemometer that measured The Big Wind in 1934 at Mount Washington Observatory
FT742-DM acoustic resonance wind sensor, one of the instruments now used to measure wind speed at Mount Washington Observatory
Anemometer on an outdoor stage set, to measure wind speed
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet. Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail.
Cup-type anemometer on a remote meteorological station
An occluded mesocyclone tornado (Oklahoma, May 1999)
Winds are part of Earth's atmospheric circulation
RAF Exeter airfield on 20 May 1944, showing the layout of the runways that allow aircraft to take off and land into the wind