The movement of air which is caused by the non-uniform heating of Earth by Sun is called as Wind

Wind Speed:

  1. Sometimes wind blows gently, refreshingly us. At other times, it blows strongly creating storms that cause widespread damages.
  2. We need measurements of two quantities : direction and speed, to give a description of the wind.

Trade Winds

  1. They move from the Subtropical High pressure Belt to the Equatorial Low Pressure Belt in the tropics lying between 30° North and 30°South Latitudes.
  2. They blow as the N.E Trades in the Northern Hemisphere and as the S.E Trades in the Southern Hemisphere.
  3. The name “Trade” is derived from a nautical expression ”to blow tread” meaning o blow along a regular path or “tread”.


  1. They move from the Sub-tropical High Pressure Belt to the Sub-polar Low Pressure Belt in the temperate latitudes lying between 30° and 60°, on either side of the Equator.
  2. They are more constant and stronger in the southern Hemisphere because there are no large landmasses to interrupt them.
  3. In places they become so strong that these winds are known as the Roaring Forties or the Brave West Winds and the Furious Fifties.
  4. The belts of the Westerlies move north and south following the sun’s movement. These are known as Westerlies because they blow out of the west.


Polar Winds

  1. They blow from the Polar High Pressure Belt to the Sub-polar Low Pressure Belt lying between latitudes 60° and the poles on both sides of the Equator.
  2. These winds blow from the east to form the Polar Easterlies.
  3. They are more regular in the Southern Hemisphere.
  4. Polar winds are extremely cold and dry because they come from the ice-cap region.


Climate Winds or Periodic Winds

These winds change their direction along with change in time or change in climate. Typical examples are the sea breezes & Monsoon winds.


Monsoon Winds

  1. Monsoon winds are seasonal winds which is distinguished by their direction completely reversal from one season to another.
  2. They blow from the sea to the land in summer.
  3. They blow from the land to the sea in winter.


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