1. El Niño / Southern Oscillation (ENSO)
By Sagar Bora
University of Bremen

2. Presented by Sagar Bora
Outline
Motivation/History
El – Niño/La Niña definition
Normal Conditions in the Pacific Ocean
El – Niño Conditions
La-Niña Conditions
Effects of El – Niño and La-Niña
El – Niño facts
Summary
9/20/2018
Presented by Sagar Bora

3. Presented by Sagar Bora
El Niño
From the mid 18th century, Peruvian fisherman noticed that their harvest completely failed every few years.
This periodic event was associated with unusually warm waters off the coast of Peru.
Since the periodic warming almost always occurred around December, the fisherman named it El Niño, in reference to the Christ child.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

4. Presented by Sagar Bora
Southern Oscillation
In the late 19th century Gilbert Walker, the head of the Indian Meteorological Service notices that the Indian monsoon fails periodically every few years, leading to drought and famine in India.
Search for a way to predict the Indian monsoon.
Identified a peculiar see-saw relationship between pressure over the maritime continent and India and the Pacific near South America.
He called this relationship the Southern Oscillation.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

5. Presented by Sagar Bora
ENSO
In 1969, UCLA professor Jacob Bjerknes was the first to recognize that El Niño and the Southern Oscillation are actually manifestations of the same physical phenomenon and that it results from an unstable interaction between the atmosphere and the ocean. This resulted in the term ENSO to refer to this phenomenon.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

6. Why should we study El Niño?
Reduced upwelling off the coast of South America. So periodic failure of fishery near Peru, which normally is responsible for one-fifth of global fish production. High coral mortality
Drought in South-east Asia, India, Australia and Africa
Heavy rainfall in the South Americas
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

7. Presented by Sagar Bora
El – Niño definition
From:
El Niño : When the three-month running mean of the Sea Surface Temperature anomalies in the Nino 3.4 region are greater than or equal to 0.5°C, an El Niño event is assumed to be taking place.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

8. Presented by Sagar Bora
La Niña definition
From:
La Niña : When the three-month running mean of the Sea Surface Temperature anomalies in the Nino 3.4 region are greater than or equal to -0.5°C, an La Nina event is assumed to be taking place.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

9. Normal Conditions in the Pacific Ocean
Nutrient rich cool water along the Peruvian coast (eastern pacific) due to upwelling;
good for marine life;
Shallow mixed layer; thermocline raised
3 to 8 °C warmer water in the west Pacific near Australia, Indonesia
Deep mixed layer; thermocline pushed down
From:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

10. Normal Conditions in the Pacific Ocean
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

11. Normal Conditions in the atmosphere
High pressure in the east above the cold water, low pressure in the west above the warmer water
Pressure gradients result in easterly trade winds which in turn results in upwelling along the Peruvian coast
Trade winds brings moist warm air towards Indonesian region which rises and travels eastward before sinking in the east. This is a thermally direct circulation found by Sir G. Walker.
The Pacific Ocean is a huge mass of water which can control many climate features in its region, since changes in the ocean result in characteristic changes in the atmosphere which, in turn, alter climate and weather patterns across the globe.
From:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

12. El – Niño Conditions in the atmosphere
Easterly winds weakens, even changes directions sometimes and becomes westerlies due to change in the sign of pressure gradient. Sir Walker called this east-west seesaw in southern Pacific pressure “Southern Oscillation”
From:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

13. El Niño conditions in the Pacific Ocean
Due to change in the wind direction, the currents on the ocean also slows down or changes direction from westward to eastward.
SST rises in the eastern pacific and the western pacific cools down a bit; Downwelling occurs off the coast of Peru; nutrient-less warm surface water leads to decline in marine life
Rainy conditions move with the warmer SST and dry conditions move with the cold
From:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

14. El Niño Conditions in the Pacific Ocean
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

15. A normal year and an El Niño year
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

16. Presented by Sagar Bora
La Niña conditions
During La Niña years, the upwelling off the Peruvian coast is enhanced and the SSTs in the Nino regions become cooler than usual.
The Walker Circulation operates in the same way as described for normal years, but because of the larger area of colder water off the South American coast and the displacement of warmer water to the west, the atmospheric pattern also shifts accordingly. Heavier rainfall over Australia and Indonesia and dry spans over South Americas
From:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

17. La Niña conditions in the Pacific Ocean
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

18. Global impacts of El Niño
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

19. Global impacts of La Niña
Source:
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

20. Presented by Sagar Bora
El Niño facts
ENSO is not a weather anomaly, it’s a part of a cycle.
Every weather anomaly throughout the world that occurs during an El Niño year is not caused by that El Niño.
The impact of global warming on El Niño is not as yet known, speculation notwithstanding.
Forecasting El Niño’s onset does not tell us much about its other characteristics (e.g., intensity, frequency, duration).
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

21. Summary and conclusions
El Niño , La Nina and the Southern Oscillations are coupled phenomenon that occurs periodically at the Pacific Ocean.
Normally, SST and SSH at the eastern pacific is lower than the western pacific.
During El Niño , it’s the opposite of the normal conditions. SST and SSH rises in the eastern pacific and easterlies slows down or changes direction.
La Niña is the extreme of the normal conditions. SST at the east coast decreases more than usual.
Both La Niña and El Niño effects the global climate and the economy of many countries.
9/20/2018
Presented by Sagar Bora
Motivation
Definitions
Normal conditions
El Nino
La Nina
Effects
Facts
Summary

22. Thank you for Listening!! Questions?
9/20/2018
Presented by Sagar Bora