Solar energy (or sun’s energy) is responsible for the blowing of wind. This can be explained as follows : The sun-rays fall on the whole earth. But the intensity of sun-rays is much more stronger near the equator of the earth than in the polar regions. Due to more intense sun-heat, the air near the surface of earth in equatorial regions becomes quite hot. This hot air, being lighter, rises upwards. The cooler air from the polar regions of the earth starts flowing towards the equatorial regions of the earth to fill the space vacated by the hot rising air.
In this way, air flows from the higher pressure regions to the low pressure regions of the earth. This flow of air from one place to another constitutes wind. The flow of air gets disturbed continuously by the rotation of earth as well as by local conditions. Due to these interacting forces, the speed of wind may vary from 5 km/h to 10 km/h of gentle breeze to the very high speed of about 800 km/h of a storm (or tornado). Thus, the strength of wind keeps on changing and it is unpredictable. From the above discussion we conclude that the three factors which are mainly responsible for the blowing of wind are :
- The uneven heating of equatorial regions and polar regions of the earth by sun-rays.
- Rotation of earth.
- Local conditions.