Wind circulation on the Earth

 Air masses are moved by solar heating and in particular by the difference in temperature (gradient) between equatorial and tropical areas.
Solar radiation in equatorial areas is more intense than in tropical areas.
Tropical air, warmer and less dense, tends to go up attracting cold air from tropical areas. When it arrives at the tropics, the warm air cools down and starts to go down. And in this way a continuous equator-poles cycle takes place. Without any other factor, the circulation of winds on the Earth would follow a regular process, like the one that has just been described.
Factors that affect wind circulation
In reality, other geographic-astronomic factors act on air circulation, modifying its movement.
The inclination of the Earth’s axis and the revolution of the Earth around the Sun seasonally displace the areas of higher irradiation between the two tropics. Moreover, the Earth’s rotation contributes to the alternation of solar irradiation and its surface, scarcely homogeneous, has a different absorption capacity and heat exchange. The Earth’s rotation causes another factor that is fundamentally important to understand the wind circulation: Coriolis’ acceleration, that produces the typical spiral or rotation movement of air masses.
Another factor determining the direction and the power of the wind is the friction on the Earth’s surface, as the wind uses energy to overcome it, as well as the presence of mountain chains, that block or divert the wind path.