In common usage, wind gradient, more specifically wind speed gradient
or wind velocity gradient,
or alternatively shear wind,
is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. It is the rate of increase of wind strength with unit increase in height above ground level. In metric units, it is often measured in units of meters per second of speed, per kilometer of height (m/s/km), which reduces inverse milliseconds (ms−1), a unit also used for shear rate.
This albatross is an expert in dynamic soaring using the wind gradient.
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