Wind is the flow of air or other gases that compose an atmosphere (including, but not limited to, the Earth's). It occurs as air is heated by the Sun and thus rises. Cool air then rushes to occupy the area from which the hot air has just moved. It can be loosely classified as a convection current.Fact: date=September 2008

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. 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.

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.

Forces

Forces which drive wind or affect it are the pressure gradient force, the Coriolis force, buoyancy forces, and friction forces. When a difference in pressure exists between two adjacent air masses, the air tends to flow from the region of high pressure to the region of low 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.

The two major driving factors of large scale global winds

Components of wind

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 winds. Examples are:

• Geostrophic wind (wind that is a result of the balance between Coriolis force and pressure gradient force; flows parallel to isobars and approximates the flow above the atmospheric boundary layer in the midlatitudes if frictional effects are low)
• Thermal wind (not actually a wind but a wind difference between two levels; only exists in an atmosphere with horizontal temperature gradients, i.e. baroclinicity)
• Ageostropic wind (difference between actual and geostrophic wind; the wind component which is responsible for air "filling up" cyclones over time)
• Gradient wind (like geostrophic wind but also including centrifugal force)

Classification

Wind terms

Gusts are short-lived increases in the strength of the wind. Conversely, when the wind decreases to less than the average wind speed, this is known as a lull. Gusts can be very brief, or can last several seconds or more. A squall is a sudden increase in wind speed which is typically associated with active weather, such as rain showers, thunderstorms, or heavy snow, but which lasts much longer than a gust. Squalls refer to an increase in the non-sustained winds over an extended time interval, as there may be lower gusts during a squall event.