Wind Patterns of the World

By Naveen Singh|Updated : August 17th, 2020

It is defined as the horizontal motion of air parallel to the pressure gradient force(PGF) and perpendicular to the isobar. It blows from the high-pressure area to low pressure area and acts as a medium for the transfer of heat and moisture from one place to another.

Global wind systems are a product of the unequal heating of the Earth’s surface.

The pressure is force per unit area, and air pressure is simply the weight (force) of the column of air above a particular location, per unit area.

Factors responsible for air pressure.

  1. Altitude.
  2. The avg. temp. Of the air above a particular location (hot air is lighter than cold air).
  3. Air composition.

Forces that affect the motion of the winds

Pressure Gradient Force:

The reason behind the PGF is the difference in the pressure between two places and acts perpendicular to the isobar. Narrowly spaced and widely spaced isobars indicate steep pressure gradient force and gentle pressure gradient force respectively.

Frictional Force:

It is defined as the force exerted by surface in the direction opposite to the direction on the wind.

Coriolis force is also reduced due to this force.

Coriolis Force: This force is produced due to the Earth’s rotation. This was first observed by the French scientist Coriolis; thus, This force is named him.

  • The intensity of the force keeps increasing with increasing distances from the equatorial belt. 
  • When wind flows in Northern sphere it deflects the in rightward direction and leftward in the southern hemisphere.
  • The Coriolis force is directly proportional to the angle of latitude. 
  • It is maximum at the poles and is absent at the equator.

Planetary Winds

  • The winds flow throughout the year from one latitude to another in response to latitudinal differences in air pressure.
  • They are global in nature.
  • They are formed because of the Latitudinal variation of atmospheric heating, the emergence of pressure belts, the migration of belts following the apparent path of the sun, the distribution of continents and oceans and rotation of the Earth.

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Trade Winds:

  • These are extremely steady winds blowing from subtropical high-pressure areas (30°N and S) towards the equatorial low-pressure belt.
  • Due to Coriolis forces and Ferrel’s law, these forces deflect to the right in Northern Hemisphere and to the left in Southern Hemisphere.
  • They are known as northeastern trades in Northern Hemisphere and southeastern trades in Southern Hemisphere. 
  • Trade winds are onshore along the eastern margin of continents and thus harbinger maritime condition especially during summer.
  • These winds form ITCZ by converging near the equator, Here these winds rise & cause heavy rainfall.

Westerly Winds:

    • They originate from the subtropical high-pressure belt and move towards the subpolar low-pressure belt and, prevail between 35° to 60 ° latitudes.
    • They are also permanent in nature and gets more powerful during winters. 
    • They transport warm and moist air toward the pole. Westerly causes formation of fronts along subpolar low-pressure zone and transport cyclone toward the western margin.
    • The British type of climate or the western European type of climate is produced by the westerly which causes rainfall throughout the year.
    • In the southern hemisphere, because of the absence of landmass, they blow with more force. 
    • They are known as roaring forties along 40°S, furious fifties along 50°S and shrieking sixties along 60°S.

Polar Easterlies :

  • The Polar easterlies blow from the Polar high-pressure area to the Temperate low-pressure area. 
  • When these winds move towards equator they are deflected westward and known as North easterlies in the Northern hemisphere and South easterlies in the Southern hemisphere These are extremely cold winds that come from the Tundra and Icecap regions of the poles. 
  • They are more regular in the southern hemisphere in comparison to the northern hemisphere. 
  • These winds converge with the warm easterlies near 60° latitudes and form the Polar front or Mid Latitude front.
  • This mid-latitude front becomes the centre of the origin of the Temperate Cyclones.

Periodic Winds/Seasonal Winds 

The change in season drives periodic winds.

e.g., Monsoons, Land and Sea Breezes, Mountain and Valley Breezes.

Monsoon Winds 

  • Monsoon winds are seasonal winds, and they also show the seasonal reversal of direction
  • ‘Flohn’ said, monsoon is a seasonal modification of general Planetary Wind System. 
  • They cause wet and dry seasons throughout much of the tropics.
  • They blow from cold to warm regions. 
  • It blows from Sea to land during summers & land to Sea during winters, due to differential in the heating of continents & oceans known as Halley’s law. 
  • In summers, the sun vertically over Tropic of cancer leads to high temp. and low pressure in central Asia, while pressure is sufficiently high at Bay of Bengal & Arabian Sea. This induces airflow from Sea to land & induces heavy rainfall in India & neighbouring countries. 
  • In winters, the sun shines vertically over the Tropic of Capricorn. Hence North-West part of India grows colder than Arabian Sea & Bay of Bengal which results in reversal of monsoon in India.
  • This theory of differential, heating was replaced by shifting of ITCZ for monsoon in India & neighbouring countries.

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Land Breeze and Sea Breeze

The land and Sea absorb and transfer heat differently due to the difference in their specific heat.

Sea breeze:

Land heats up faster during the day and becomes warmer than the Sea. Therefore, warm air rises over the land giving rise to a low-pressure area, whereas the Sea is relatively cool, and the pressure above the Sea is relatively high. 

The pressure gradient emerging from Sea to land due to the difference in the pressure between Sea and land during day time triggers the wind to blow from Sea to ground. This wind is called a. 

Land Breeze:

During the night, the land loses heat faster and becomes colder than the Sea. Now the pressure gradient is from the land to the Sea which triggers the wind to blow from land to Sea.

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