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.
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).
Ancient religions…
As a natural force, the wind was often personified as one or more wind gods or as an expression of the supernatural in many cultures. There are many different gods of wind in different religions. Vayu is the Hindu God of Wind. The Greek wind gods include Boreas, Notus, Eurus, and Zephyrus. Aeolus, in varying interpretations the ruler or keeper of the four winds, has also been described as Astraeus, the god of dusk who fathered the four winds with Eos, goddess of dawn. The Ancient Greeks also observed the seasonal change of the winds, as evidenced by the Tower of the Winds in Athens. Venti are the Roman gods of the winds. Fūjin, the Japanese wind god and one of the eldest Shinto gods. According to legend, he was present at the creation of the world and first let the winds out of his bag to clear the world of mist. In Norse mythology, Njord is the god of the wind. There are also four dvärgar (Norse dwarves), named Norðri, Suðri, Austri and Vestri, and probably the four stags of Yggdrasil, personify the four winds, and parallel the four Greek wind gods. Stribog is the name of the Slavic god of winds, sky and air. He is said to be the ancestor (grandfather) of the winds of the eight directions.
Bible
The winds are discussed in the Bible:
Winds – blowing from the four quarters of heaven (Jer. 49:36; Ezek. 37:9; Dan. 8:8; Zech. 2:6). The east wind was parching (Ezek. 17:10; 19:12), and is sometimes mentioned as simply denoting a strong wind (Job 27:21; Isa. 27:8). This wind prevails in Israel from February to June, as the west wind (Luke 12:54) does from November to February. The south was a hot wind (Job 37:17; Luke 12:55). It swept over the Arabian peninsula. The rush of invaders is figuratively spoken of as a whirlwind (Isa. 21:1); a commotion among the nations of the world as a striving of the four winds (Dan. 7:2). The winds are subject to the divine power (Ps. 18:10; 135:7). [58]
History
Kamikaze (神風) is a Japanese word, usually translated as divine wind, believed to be a gift from the gods. The term is first known to have been used as the name of a pair or series of typhoons that are said to have saved Japan from two Mongol fleets under Kublai Khan that attacked Japan in 1274 and again in 1281. Protestant Wind is a name for the storm that deterred the Spanish Armada from an invasion of England in 1588, or the favourable winds that enabled William of Orange to invade England in 1688.
