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Friday, 31 July 2020

Atmospheric pressure and winds

Atmospheric pressure and winds
Global variations in the atmospheric pressure lead to the formation of winds. The horizontal movement of air from a high-pressure zone to a low-pressure zone is called wind. There are different types of winds on the earth's surface, ranging from the light breeze that makes the leaves flutter to cyclones that cause widespread damage. Winds are named on the basis of the direction from which they blow. For example, the south wind is the wind blowing from the south. The peculiarities of the source regions influence the nature of the wind. 
Winds blowing from the sea will be saturated with moisture whereas the moisture content will be less in winds blowing from drier regions. 
Take a look at some of the general characteristics of winds.
• Names are given to winds mostly on the basis of the direction from which they blow. For example, the wind blowing from the land is called land breeze and the wind blowing in a southeasterly direction is called Southeasterly winds.
• As the winds from the oceans are saturated with water vapour they give rain. The wind-free of water vapour would be dry.
• Due to the earth's rotation a change in the direction of winds occurs. 


The speed and direction of the wind:
The factors that influence the speed and direction of winds are:
• Pressure gradient force
• Coriolis effect
• Friction

Pressure gradient
Atmospheric pressure is not uniform everywhere on the earth's surface. The change in pressure with horizontal distance is termed as pressure gradient. The pressure gradient is said to be steeper when the pressure difference is more. 

Coriolis Effect
Freely moving bodies get deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is due to the force generated as a result of Earth's rotation which is known as the Coriolis force. This force increases as it moves towards the Poles from the Equator.
Admiral Ferrell was an American scientist who studied the Coriolis effect. The law formulated by Ferrell on the deflection of winds under the influence of the Coriolis effect as indicated above is known as the Ferrell's Law.

Friction
The wind blows at high speeds over parts of the earth's surface that are flat. The reason for this is that in flat portions of the earth's surface wind undergoes only less friction. In irregular surfaces, the wind is subjected to greater friction. Due to this, the velocity of wind decreases.


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