Transcript El Nińo/Southern Oscillation - pep

El Niño / Southern Oscillation
(ENSO)
By Sagar Bora
University of Bremen
Outline
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Motivation/History
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El – Niño/La Niña definition
Normal Conditions in the Pacific Ocean
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El – Niño Conditions
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La-Niña Conditions
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Effects of El – Niño and La-Niña
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El – Niño facts
Summary
7/16/2015
Presented by Sagar Bora
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El Niño
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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.
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
3
La Nina
Effects
Facts
Summary
Southern Oscillation
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7/16/2015
Motivation
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.
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
4
La Nina
Effects
Facts
Summary
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.
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
Why should we study El Niño?
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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
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
El – Niño definition
From: www.weathersa.co.za
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.
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
7
La Nina
Effects
Facts
Summary
La Niña definition
From: www.weathersa.co.za
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.
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
8
La Nina
Effects
Facts
Summary
Normal Conditions in the Pacific Ocean
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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: www.weathersa.co.za
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
9
La Nina
Effects
Facts
Summary
Normal Conditions in the Pacific Ocean
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
Normal Conditions in the atmosphere
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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.
From: www.weathersa.co.za
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
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: www.weathersa.co.za
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
12
La Nina
Effects
Facts
Summary
El Niño conditions in the Pacific Ocean
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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: www.weathersa.co.za
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
13
La Nina
Effects
Facts
Summary
El Niño Conditions in the Pacific Ocean
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
A normal year and an El Niño year
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
La Niña conditions
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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: http://www.wrh.noaa.gov/
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
La Niña conditions in the Pacific Ocean
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
Global impacts of El Niño
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
Global impacts of La Niña
Source: http://www.wrh.noaa.gov/fgz/science/elnino.php?wfo=fgz
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
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La Nina
Effects
Facts
Summary
El Niño facts
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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).
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
20
La Nina
Effects
Facts
Summary
Summary and conclusions
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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.
7/16/2015
Motivation
Presented by Sagar Bora
Definitions
Normal conditions
El Nino
21
La Nina
Effects
Facts
Summary
Thank you for Listening!!
Questions?
7/16/2015
Presented by Sagar Bora
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