This document discusses monsoons and their causes. It defines monsoons as seasonal reversals of wind direction caused by temperature differences between land and sea. Monsoons occur due to changes in atmospheric pressure from different heating and cooling rates of continents and oceans. India's climate is dominated by monsoons, which bring most of the country's annual rainfall from June to September. There are two main types of monsoons in India: southwest monsoons which blow from the Indian Ocean, and northeast monsoons which blow from Siberia. The document also explains El Nino and La Nina phenomena and their effects on global weather patterns.

1. Kurukshetra University, Kurukshetra
Department of Environment Science
Submitted BY :-
Name : Vikrant saini
Class : MSC(P)
Roll no . 4
Submitted To :-
Prof. Smita chaudhary
Director of Department
Environment science

3. Contents
• Definition
• Cause
• Indian Monsoons
• Types of Monsoons
• El Nino and Effects
• La Nina and Effects
• Conclusion

4. Monsoons
• Monsoon is term derived from the Arabic word “Mausim”,
meaning season. It was first used by Arabic navigators to
describe the seasonal winds of Arabian sea.
• These winds blow from the north-east for one half of the year
and for the south-west of other half.

5. Cause
•Monsoons occur due to changes in atmospheric pressure which are
caused by different rates of heating and cooling of continents and oceans.
• Monsoons occur every year in many countries around the world other
than South Asia - northern Australia, Africa, South America and the US
are also affected.

6. •The Indian monsoons :
•India’s climate is dominated by monsoon.
•The term technically describes seasonal reversals of wind
direction caused by temperature differences between land and
sea breeze ,creating zones high and low pressure over land in
different seasons.

7. Types of monsoons :Types of monsoons
•South west
monsoons
•North east monsoons

8. South west monsoons :-
The South –West (summer) monsoon has warm
winds blowing from Indian Ocean. Its span is June to
September, with 75 % of the annual rainfall in India. It
varies from 10 cm in western Rajasthan to over 900 cm in
Meghalaya.

9. North east monsoons :-
North- East (winter) monsoon is characterized
by a dry continental air mass blowing from the vast
Siberian high pressure area from December to March. The
rainfall includes snowfall during winter monsoon which is of
the order of 1000 km2 in India. This is also known as
Retreating monsoon.

10. Map : 17th June 2013

11. • El Nino refers to the large-scale ocean-atmosphere
climate phenomenon linked to a periodic warming of at
least 0.5°C in sea-surface temperatures across the
central and east-central equatorial Pacific.
El Nino:
Normal conditions EL Nina conditions

12. Normal conditions :-

13. EL Nino effect :Weak trade winds and weak upwelling
cause warm water off the coast of S. America.

14. Effect of EL Nino :-
1.Dry conditions:-

15. 2. Flood conditions :-

16. La Nina:- La Nina refers to the periodic cooling normal by 3–5 °C of
ocean surface temperatures in the central and east-central
equatorial Pacific.
Normal conditions La Nina conditions

17. La Nina :-

18. Conclusion
• A monsoon is a seasonal shift in the prevailing wind
direction, that usually brings with it a different kind
of weather.
• Monsoons are large-scale sea breezes .
• El Niño and La Niña are naturally occurring
phenomena that result from interactions between
the ocean surface and the atmosphere over the
tropical Pacific.

19. References
 Contents – Monsoons
http://www.monsoons.com
 Contents - El Niño
http://www.msc-smc.ec.gc.ca/education/elnino/index
 El Niño/La Niña Update
http://www.wmo.ch/nino/updat.html#intro

20. Any Question ?