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Wind is the flow of air or other gases that compose an atmosphere (including, but not limited to, the Earth's ). Wind is air molecules in motion on Earth. In outer space, the solar wind is the movement of gases or charged particles from the sun through space, while the planetary wind is the outgasing of light elements from a planet 's atmosphere into space. Differences in density between two air masses lead to wind. Differential heating between the poles and the equator lead to the development of the jet stream and the associated climatological mid-latitude westerlies , polar easterlies , and the trade winds . Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them, the geographic regions in which they occur, and their effect. Wind speeds over much of the globe are measured over a ten-minute time frame, with the United States and India using different averaging intervals. Winds are plotted on surface weather analyses within station models, indicating the direction the wind is blowing from as well as its strength.
Wind speeds have various names associated with their average strength, such as breeze, gale , storm , hurricane , and typhoon. Wind gusts exceed the minimum value over the observed time frame. Winds which sharply increase and last for a minute are termed squalls . While wind is often a standalone weather phenomenon, it can also occur as part of a storm system , most notably in a cyclone . Winds can shape landforms, via a variety of aeolian processes . Wind occurs on a range of scales, from local breezes generated by heating of land surfaces and lasting tens of minutes, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth . The two major driving factors of large scale atmospheric circulation are the differential heating between the equator and the poles, which causes the jet stream , and the rotation of the planet ( Coriolis effect ) which causes the circular motion of air around areas of high and low pressure .
In human civilization , wind has inspired mythology , changed the course of history , expanded the range of transport and warfare , and provided a power source for mechanical work , electricity , and recreation . Wind has been used to steer sailing ships across vast oceans. By air, hot air balloons use the wind to take short trips. Airships have historically been used for longer trips, but nowadays are used for a variety of monitoring efforts such as during public sporting events and drug trafficking efforts. Areas of wind shear caused by various weather phenomena can lead to dangerous situations for airplanes . Nature uses wind to help disperse seeds from various plants, in order to enable the survival of those plant species. Dust from large deserts can be moved large distances from their source region by the prevailing winds

Cause
Surface analysis of Great Blizzard of 1888 on March 12, 1888 at 10 pm. Areas showing greater packing of isobars indicate the area of greater pressure difference, and higher winds.
The first scientific description of wind was from the seventeenth-century Italian physicist Evangelista Torricelli ,
... winds are produced by differences of air temperature, and hence density, between two regions of the earth.
Forces which drive wind or affect it are the pressure gradient force , the coriolis force, buoyancy forces, and friction forces. When a difference in density exists between two adjacent air masses, the air tends to flow from the regions of higher to lower pressure. On a rotating planet, flows will be acted upon by the Coriolis force , in regions sufficiently far from the equator and sufficiently high above the surface. Surface friction with land causes winds to blow more inward into low pressure areas.
The two major driving factors of small room or large scale global winds are the differential heating between the equator and the poles (difference in absorption of solar energy between these climate zones ), and the rotation of the planet. It is the differential heating between the poles and the equator that lead to the development of the jet stream .
Winds defined by an equilibrium of physical forces are used in the decomposition and analysis of wind profiles. They are useful for simplifying the atmospheric equations of motion and for making qualitative arguments about the horizontal and vertical distribution of moving you winds. Geostrophic wind is the wind component that is a result of the balance between Coriolis force and pressure gradient force. It flows parallel to isobars and approximates the flow above the atmospheric boundary layer in the midlatitudes if frictional effects are low.
The Thermal wind is not actually a wind but a wind difference between two levels; only exists in an atmosphere with horizontal temperature gradients , i.e. baroclinicity .
Ageostrophic wind is the difference between actual and geostrophic wind,
or the wind component which is responsible for air "filling up" cyclones over time. The Gradient wind is similar to the geostrophic wind but also includes centrifugal force (or centripetal acceleration ).
Measurement
A windmill style of anemometer
Wind direction is reported by the direction from which it originates. For example, a northerly wind blows from the north to the south.
Anemometers measure wind speed , either directly, e.g. with rotating cups, or indirectly, e.g. via pressure differences or the propagation speed of ultrasound signals.
Its associated weather vane (also known as a wind vane) is used to indicate wind direction.
Pitot tubes use the pressure differential between an inner tube and an outer tube (which is exposed to the wind) to determine the dynamic pressure, which can be used to compute the wind speed.
At airports, windsocks are primarily used to indicate wind direction, but can also be used to estimate wind speed by its angle of hang.
Sustained wind speeds which are reported globally at a 10 metres (33 ft) height, and are averaged over a 10 minute timeframe. The United States reports winds over a 2 minute average,
while India typically reports winds over a 3 minute average.
This is an important distinction, as the value of a one-minute sustained wind is 14% greater than a ten-minute sustained wind.
Wind gusts are defined as maxima which exceed the lowest wind speed measured during a 10 minute time interval by 10 knots (19 km/h). A squall is a doubling of the wind speed above a certain threshold, which lasts for a minute or more.
To determine winds aloft, rawinsondes determine wind speed by GPS or radar tracking of the probe.
Alternatively, movement of the parent weather balloon position can be tracked from the ground visually via a theodolite , with the wind profile is computed from drift rate and the theoretical speed of ascent.
Remote sensing techniques for wind include SODAR , Doppler LIDARs and RADARs which can measure the Doppler shift of electromagnetic radiation scattered or reflected off suspended aerosols or molecules , and radiometers and radars can be used to measure the surface roughness of the ocean from space or airplanes. This measurement can be used to estimate wind velocity close to the sea surface over oceans. Wind Engineering describes the study of the effects of the wind on the built environment, including buildings, bridges and other man-made objects

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