The Wind is air movement

Wind is the flow of gases across the surface of the Earth and consists of bulk air motion. It's caused by differences in atmospheric pressure and when there are differences then the air moves from higher to lower pressure areas, resulting in different rates. It's determined by the speed, the types of forces that cause it, spatial scale, the regions in which they occur and their impact. There are various aspects such as speed, density of the gas present and share power. Often referred to by the strength and the direction from which the wind is blowing. Rarely blowing constant speed, actually changes the intensity. Exceptions are the monsoons that blow through part of the constant direction and intensity, in certain parts of the Earth. The strength can be approximately evaluated and to effect the objects in nature.

The configuration of the soil also affects the strength and direction with the ratio of pressure in the atmosphere, the presence of natural barriers and overgrown terrain (friction with the ground). This creates a terrain formed fertile ground, scatter the seeds of various plants, the spread of fire and more. The two main driving factors of large winds are differential heating between the equator and the poles (the difference in the absorption of solar energy leads to buoyancy forces) and the rotation of the planet. Outside the tropics and above, the effect of friction on the surface, big winds tend to make a balance. Near the planet's surface friction causes the wind is slower than it would be otherwise. Surface friction also causes the winds are more inward in the area of low pressure.

Short-term high-speed winds are called strikes and long-term have different names associated with their average strength, such as breeze, gale, storms and hurricanes. It occurs at various levels, from the thunderstorm for a few tens of minutes, to local breezes generated by heating of land and takes a couple of hours, to global winds resulting from the difference in the absorption of solar energy between the climate zones on Earth. Those who blow close to the ground are local and high winds are at a great distance. There are solar and planetary winds. Solar are moving charged particles or gases from the Sun through space and planetary the degassing of light chemical elements from a planet's atmosphere into space.

Classifications with speed:

- Calm (up to 2 km / h)
- Light air (2-6 km / h)
- Light breeze (7-11 km / h)
- Gentle breeze (13-19 km / h)
- Moderate breeze (20-30 km / h)
- Fresh breeze (31-39 km / h)
- Strong breeze (41-50 km / h)
- Moderate gale (52-61 km / h)
- Fresh gale (63-74 km / h)
- Strong gale (76-87 km / h)
- Whole gale (89 to 102 km / h)
- Storm (104-117 km / h)
- Hurricane (119-222 and more km / h)

Power of wind:

Energy of wind is the kinetic energy of the air in motion. The kinetic energy of a packet of air of mass m with velocity v is given by ½ m v2. To find the mass of the packet passing through an area A perpendicular its velocity (which could be the rotor area of a turbine), we multiply its volume after time t has passed, with the air density ρ, which gives us m = A v t ρ. Total wind energy is:

Differentiating with respect to time to find the rate of increase of energy, we find that the total wind power is:

Power of wind is thus proportional to the third power of the wind velocity.