The document provides an overview of wind systems, defining wind as air in motion caused by atmospheric pressure differences. It classifies winds into primary, secondary, and tertiary types, with a focus on primary winds such as trade winds, westerlies, and polar easterlies, describing their characteristics and patterns. Key factors influencing planetary wind patterns include latitudinal temperature variations, pressure belt emergence, the distribution of land and water, and the Earth's rotation.

1. Wind System
Lecture-1

2. Wind System
Wind System:
 The air in motion is called wind.
 Air is set in motion due to the differences in atmospheric pressure.
 Wind blows from high pressure to low pressure.
 Wind measurement instruments are :
 Wind vane on weather cock - measures wind direction
 Anemometer - measures wind velocity

3. Wind System

4. Wind System
 Types of Winds:
Winds can be classified in three types :
 Primary Winds
 Secondary Winds
 Tertiary Winds

5. Wind System
Primary Winds:
 Other names: Prevailing Winds/Planetary Winds/Permanent
Winds/Invariable Winds.
 Permanent - blow constantly in same direction throughout the year.
 Planetary Winds - flow from one latitude to another latitude (larger areas on
earth).

6. Wind System
There are three main types primary winds :
 Trade winds.
 Westerlies and
 Polar Easterlies

7. Wind System
Trade Winds:
 Flow in Hadley Cells in both the hemispheres.
 Flow from Sub tropical High Pressure Belts towards Equatorial Low
Pressure Belt between 30° N and 30° S latitudes.
 Flow towards the equator from the north-east in Northern Hemisphere
and from the south- east in Southern Hemisphere.

8. Wind System

9. Wind System
 Trade winds are descending and stable at the surface of their origin (Sub
tropical high Pressure belts).
 On their way to Equator, they get warm and moist and near Equator they
converge, rise and cause heavy rains.

10. Wind System
Westerlies:
 The are more constant and stronger in the southern hemisphere because there is
no large landmasses to interrupt them.
 The westerlies are best developed between 40° and 65°S latitudes.
 These latitudes are often called:
• Roaring Forties
• Furious Fifties
• Shrieking Sixties

11. Wind System

12. Wind System
Polar Easterlies:
 These dry & cold winds flow in Polar Cells in both the hemispheres.
 Flow from Polar High Pressure Belts towards Sub-polar Low Pressure Belt
between 90° (Poles) and 60° latitudes in both the hemispheres.
 It blows from north-east to south-west direction in Northern
Hemisphere and south-east to the north-west in Southern Hemisphere.

13. Wind System

14. Wind System
Factors Governing Pattern of Planetary Winds:
 Latitudinal variation of atmospheric heating.
 Emergence of pressure belts.
 The migration of belts following apparent path of the sun.
 The distribution of continents and oceans.
 The rotation of earth.

15. Wind System
Conclusion: