PPT: Permanent Winds | Geography for UPSC CSE PDF Download

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Classification of Winds • Permanent winds or Primary winds or Prevailing winds or Planetary 
Winds • The trade winds, westerlies and easterlies.
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Classification of Winds • Permanent winds or Primary winds or Prevailing winds or Planetary 
Winds • The trade winds, westerlies and easterlies. Primary Winds or Prevailing Winds or 
Permanent Winds or Planetary Winds
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Classification of Winds • Permanent winds or Primary winds or Prevailing winds or Planetary 
Winds • The trade winds, westerlies and easterlies. Primary Winds or Prevailing Winds or 
Permanent Winds or Planetary Winds Trade Winds • The trade winds are those blowing from the sub-tropical high 
pressure areas towards the equatorial low pressure belt. • Therefore, these are confined to a region between 30°N and 30°
S throughout the earth’s surface. • They flow as the north-eastern trades in the northern hemisphere and 
the south-eastern trades in the southern hemisphere. • This deflection in their ideally expected north-south direction is explained 
on the basis of Coriolis force and Farrel’s law. • Trade winds are descending and stable in areas of their origin 
(sub-tropical high pressure belt), and as they reach the equator, they 
become humid and warmer after picking up moisture on their way. • The trade winds from two hemispheres meet at the equator, and due to 
convergence they rise and cause heavy rainfall. • The eastern parts of the trade winds associated with the cool ocean 
currents are drier and more stable than the western parts of the ocean.
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Classification of Winds • Permanent winds or Primary winds or Prevailing winds or Planetary 
Winds • The trade winds, westerlies and easterlies. Primary Winds or Prevailing Winds or 
Permanent Winds or Planetary Winds Trade Winds • The trade winds are those blowing from the sub-tropical high 
pressure areas towards the equatorial low pressure belt. • Therefore, these are confined to a region between 30°N and 30°
S throughout the earth’s surface. • They flow as the north-eastern trades in the northern hemisphere and 
the south-eastern trades in the southern hemisphere. • This deflection in their ideally expected north-south direction is explained 
on the basis of Coriolis force and Farrel’s law. • Trade winds are descending and stable in areas of their origin 
(sub-tropical high pressure belt), and as they reach the equator, they 
become humid and warmer after picking up moisture on their way. • The trade winds from two hemispheres meet at the equator, and due to 
convergence they rise and cause heavy rainfall. • The eastern parts of the trade winds associated with the cool ocean 
currents are drier and more stable than the western parts of the ocean. Westerlies • The westerlies are the winds blowing from the sub-tropical high 
pressure belts towards the sub polar low pressure belts. • They blow from south-west to north-east in the northern 
hemisphere and north-west to south-east in the southern 
hemisphere. • The westerlies of the southern hemisphere are stronger and 
persistent due to the vast expanse of water, while those of the 
northern hemisphere are irregular because of uneven relief of vast 
land-masses. • The westerlies are best developed between 40° and 65°S latitudes. 
These latitudes are often called Roaring Forties, Furious Fifties, and 
Shrieking Sixties – dreaded terms for sailors.
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Classification of Winds • Permanent winds or Primary winds or Prevailing winds or Planetary 
Winds • The trade winds, westerlies and easterlies. Primary Winds or Prevailing Winds or 
Permanent Winds or Planetary Winds Trade Winds • The trade winds are those blowing from the sub-tropical high 
pressure areas towards the equatorial low pressure belt. • Therefore, these are confined to a region between 30°N and 30°
S throughout the earth’s surface. • They flow as the north-eastern trades in the northern hemisphere and 
the south-eastern trades in the southern hemisphere. • This deflection in their ideally expected north-south direction is explained 
on the basis of Coriolis force and Farrel’s law. • Trade winds are descending and stable in areas of their origin 
(sub-tropical high pressure belt), and as they reach the equator, they 
become humid and warmer after picking up moisture on their way. • The trade winds from two hemispheres meet at the equator, and due to 
convergence they rise and cause heavy rainfall. • The eastern parts of the trade winds associated with the cool ocean 
currents are drier and more stable than the western parts of the ocean. Westerlies • The westerlies are the winds blowing from the sub-tropical high 
pressure belts towards the sub polar low pressure belts. • They blow from south-west to north-east in the northern 
hemisphere and north-west to south-east in the southern 
hemisphere. • The westerlies of the southern hemisphere are stronger and 
persistent due to the vast expanse of water, while those of the 
northern hemisphere are irregular because of uneven relief of vast 
land-masses. • The westerlies are best developed between 40° and 65°S latitudes. 
These latitudes are often called Roaring Forties, Furious Fifties, and 
Shrieking Sixties – dreaded terms for sailors. Polar easterlies • The Polar easterlies are dry, cold prevailing winds blowing 
from north-east to south-west direction in Northern Hemisphere 
and south-east to north-west in Southern Hemisphere. • They blow from the polar high-pressure areas of the sub-polar lows.