Brief discussion of ENSO, its three faces and specially concerning the la nina, how it occurs, what are the impacts of la nina by Deepak gauniyal.

1. LA NINA
PAPER- ADVANCED CLIMATOLOGY
SUBMITTED TO
SUBMITTED BY
Prof. MS NEGI DEEPAK

2. CONTENT
 Introduction
 The three phases of ENSO
 What is la Nina
 Why la Nina occurs?
 Typical La Nina Impacts
 Impacts on Indian climate
 Conclusion
 Reference

3. INTRODUCTION
 El Nino and La Nina events are a natural part of the global climate
system. They occur when the Pacific Ocean and the atmosphere
above it change from their neutral(normal) state for several
seasons.
 El Nino events are associated with a warming of the central and
eastern tropical Pacific, while La Nina events are the reverse, with a
sustained cooling of these same areas.
These changes in the Pacific Ocean and its overlying atmosphere
occur in a cycle in a known as the El Nino- Southern Oscillation
(ENSO).

4. THE THREE PHASES OF THE (ENSO)
The neutral phase
• In the neutral state trade winds blow east to west asross the
surface of the tropical Pacific Ocean, bringing warm moist air and
warmer surface waters towards the western Pacific and keeping
the central Pacific Ocean relatively cool. The thermocline is deeper
in the west than east.
El Nino
• During an El Nino event, trade winds weaker or may even
reverse,allowing the area of warmer than normal water to move
into the central and eastern tropical Pacific Ocean.

7. LA NINA
• La Nina means The little Girl in Spanish.
• La Nina is also sometimes called El Viejo, anti-El Nino, or simply “a
cold event’’.
• During a La Nina event, the walker circulation intensifies with
greater convection over the western Pacific and stronger trade
winds.
• La Nina episodes represent periods of below- everage sea surface
temperatures across the east-central Equqtorial Pacific. Global
climate La Nina impacts tends to be opposite those of El Nino
impacts
• During a La Nina year, winter temperature is warmer than normal
in the southeast and cooler than normal in the western Pacific.

8. • Unusually cold ocean temperatures in the equatorial western
Pacific.
• During a period of La Nina, the sea surface temperature across the
equatorial Eastern Central Pacific Ocean will be lower than normal
by 3 to 5 degree.
• It has extensive effect on the weather across the globe.
Upwelling
Upwelling is a vertical motion of water. When winds and currents
displace water at the surface of ocean, water from deeper in the
ocean is drawn up to replace the displaced water. Deep water is
generally cooler and richer in nutrients than surface water so
upwelling is important in supporting productivity in the oceans of
the world.

10. WHY LA NINA OCCURS
 Occur due to increases in the strength of the normal patterns of
trade wind circulation.
 Under normal condition, these winds move westward, carrying
warm surface water to Indonesia and allowing cooler water to
upwell along the south American coast.
 Periodically these trade winds are strengthened, increasing the
amount of cooler water towards the coast of south America to esat
Australian coast.
 Causes cooler water increases in the deep cloud buildup towards
suotheast asia.
 Resulting in wetter than normal conditions over Indonesia during
the northern hemisphere winter.

11. TYPICAL LA NINA IMPACTS
During a La Nina year, winter temperatures are warmer than normal
in the southeast and cooler than normal in the northwest pacific.
1. Increased Rainfall
2. Catastrophic floods
3. Drier than normal condition
4. Increased commercial fishing
5. Affects the climate patterns
6. Droughts in Ecuador and Peru

12. Impacts on Indian climate
 La Nina results in better than normal monsoon in india.
 Good crop production in india during La Nina period.
 La Nina during winter causes more cold conditions over
the Indian subcontinent.
 India experienced more rainfall during la Nina years
2011.
 Increases the number of hazards such as heavy rain
and floods.

13. Conclusion
La Nina is caused by an interaction between the Pacific
Ocean and the atmosphere above . However it can have
effects on weather all over the world. El Nino and La Nina
develop in the Tropical Pacific Ocean. La Nina brings heavy
rains to the western Pacific coasts and during that time
eastern Pacific faces drought. Scientific progress on the
understanding and modelling of this phenomenon has
improved prediction skills to within a range of one to nine
months in advance, giving society the opportunity to
prepare for associated hazards such as heavy rains, floods
and drought.

14. REFERENCE
La Nina Theme Page
http://www.pmel.noaa.gov/tao/elnino/nino-home.htm
La Nina : online meteorology guide
http://www2010.atmos.uiuc.edu/(gh)/guides/mtr/eln/home.rxml
Contents – La Nina
http://www.msc-smc.ec.gc.ca/education/elnino/index
El Nino/La Nina Update
http;//www.wmo.ch/nino/update.html/intro

15. THANK YOU