This presentation basically gives information about Surface wind systems of Earth's atmosphere.

1. Presentation On:
By- Ankit Abhilash Swain
CUJ/M/2018/CEVS/06

2. Contents:
• Introduction
• Broad categories of Atmospheric motion
 Primary circulation
 Secondary circulation
 Tertiary circulation
• Earth Surface Wind System
 Doldrums
 Trade wind belts
 Prevailing westerlies
 Polar easterlies
• Conclusion
• References

3. Introduction
• The earth’s surface get differentially heated due to the varying
amount of isolation received by it.
• Temperature difference thus produced account for the density
difference that drives the atmosphere in 3-dimensional motion on
globe.
• The general circulation of earth depends on many factors, like;
 Isolation
 Orbit of the earth
 Revolution of earth around sun
 Geographical conditions

4. • Winds are the means by which atmosphere tries to balance out
the uneven distribution of temperature over the earth surface.
• Besides the advectional transport of heat energy over the earth
surface, winds also carry out water vapour from over the water
bodies to land surface.
• Winds are generally of two types and flows in two regions:
i. Equatorial region (progressively hotter)
ii. Polar region (progressively colder)

5. Broad Categories of Atmospheric Motion
• The earth atmospheric motion is generally categorised
into three broad categories;
i. Primary circulation
ii. Secondary circulation
iii. Tertiary circulation

6. • Primary circulation:
 Macro-scale circulation.
 Includes planetary wind system(trade winds, westerlies and easterlies).
 Primary circulation pattern which prepare broad framework for other circulation
patterns.
• Secondary circulation:
 Synoptic-scale circulation.
 Consist of cyclones, anticyclones, monsoon and air masses.
• Tertiary circulation:
 Both Meso-scale and micro-scale circulation.
 Includes the local winds which are produced by local causes and which only
affect the weather and climate of particular locality or area.

7. Earth Surface Wind System
• This wind system is of primary type of atmospheric
circulation.
• The earth surface wind system is divided into four types of
wind pattern, i.e.;
a) Doldrums
b) Trade wind belts
c) Prevailing westerlies
d) Polar easterlies

8. • The general scheme of circulation is shown in the figure.

9. Doldrums
• Equatorial belt of calm and variable wind lying over the
equatorial region.
• Lies in between 5°N and 5°S latitude.
• Low pressure zone.
• Flow of wind is pole ward.
• Receives highest isolation.
• Meeting place of two trade winds, also called as Inter-
tropical convergence zone.

10. Doldrums
equator
5°N
5°S
0°
Equatorial Low
pressure zone
90°N
90°S

11. Trade wind belts
• Trade winds originate because of the pressure gradient from the
sub-tropical belts of high pressure to the equatorial belt of low
pressure.
• Also known as Horse latitudes.
• Extends from 5°to 30°of latitude in both of the hemisphere i.e.;
northern and southern hemisphere.
• Wind flows equator ward.
• Winds from northern hemisphere are called as Northeast trade
winds, similarly from southern hemisphere are called as
Southeast trade winds.
• This zone is also called as Hadley cell.

12. Trade wind belts
5°N
5°S
equator
0°
90°N
90°S
30°N
30°S
35°S
35°N
Sub-tropical high
pressure zone

13. Prevailing westerlies
• Lies between 30°and 60°latitude in each hemisphere i.e.; northern and
southern hemisphere.
• Its move out from the pole ward margins of sub-tropical high-pressure belts.
• In northern hemisphere due to large percentage of land area with high
mountains, plateaus and changing seasonal pressure system, the westerly
flows is nearly observed.
• But in case of southern hemisphere, where there is preponderance of water
over land, the westerlies are stronger and retain their direction persistency.
• In the southern hemisphere, between the latitude of 40°and 60°there is all
water. Here the westerlies are powerful and persistence that the sailor used
such expressions as, “roaring forties”, “furious fifties” and “screaming sixties”
for these high velocity wind in the latitude belts of forties, fifties and sixties
respectively.

14. 0°
30°N
60°N
60°s
30°S
equator
90°N
90°S
Prevailing
westerlies
Prevailing westerlies

15. Polar easterlies
• It moves out of the polar high towards the sub-polar low
pressure belt.
• Lies between 60°and 90°latitude in each hemisphere.
• They flow from various direction and they are largely
controlled by local weather distribution.
• Polar easterlies of the southern hemisphere are rather
more coherent and well-defined.

16. 90°N
90°S
equator
0°
60°N
65°N
60°S
65°S
Polar
easterlies
Polar easterlies

17. • Climatology, D. S Lal
• Balasubramanian, A. (2017). SCOPE OF STUDYING
CLIMATOLOGY. 10.13140/RG.2.2.16027.77600.
References

18. Thank You..