Wind in simple terms is nothing but a moving air. We all enjoy wind rustling through the leaves in our garden. It has also expanded the range of transport and has provided power source in terms of mechanical energy for the generation of electricity in wind mills and recreation purposes in hot air balloons. Wind power was also used in voyages by sailors to direct their ships. When the winds are strong, they lead to destruction of life and property in the form of cyclones and storms, causing forest fires, landslides etc. In this article we will learn about the causes of wind and the destruction caused by winds.
Causes of Wind
The main cause of generation of wind is the uneven heating of two regions. Following are the examples of uneven heating we see around us:
Uneven heating between land and sea:
Sea water gets heated more slowly as compared to land. As the temperature of the land rises, the air above it gets heated by conduction. The density of warm air is less than the surrounding environment, because of which it rises, creating a vacuum in its place. The cooler air from the sea rushes to fill the vacuum which creates a cool coastal breeze. At night, the land cools off more quickly, which creates a temperature difference between the temperature onshore and that offshore. Because of this temperature difference, again a pressure drop is created establishing a land breeze.
Flow of Air between Land and Sea
Uneven heating between equator and pole:
The equatorial and tropical regions (close to the equator) get the maximum heat from the sun; hence they get hotter than the polar regions. The air surrounding this region gets heated up and rises to create vacuum. Cooler air from the poles rushes to fill the vacuum. The wind does not flow in the north-south direction because a change in direction is caused by the rotation of the earth.
Flow of Air between Equator and Pole
Types of Wind
Wind blowing above the earth surface may be classified into four major types:
- Planetary winds
- Monsoon winds
- Cyclones and thunderstorms
- Local winds
Planetary winds: Planetary winds comprise winds distributed throughout the lower atmosphere. The winds blow regularly throughout the year confined within latitudinal belts, mainly in north-east and south-east directions or from high pressure polar-regions to low pressure regions.
Monsoon winds: The temperature difference created due to the Indian Ocean, Arabian Sea and Bay of Bengal on one side and Himalayan wall on the other forms the basis of monsoons in the Indian subcontinent.
Cyclones and thunderstorms: Cyclones are defined as mass of air that rotates around the center of low pressure on a large scale and thunderstorms are strong winds accompanied by tornadoes, hail, thunder, heavy rains and lightening.
Local winds: The local winds include the sea and land breeze created due to the pressure difference between the air over the sea and the land regions.
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