El Nio Southern Oscillation ENSO - PowerPoint PPT Presentation

1 / 22
About This Presentation
Title:

El Nio Southern Oscillation ENSO

Description:

Presented by Sagar Bora. Normal Conditions in the Pacific Ocean ... Presented by Sagar Bora. El Ni o facts. ENSO is not a weather anomaly, it's a part of a cycle. ... – PowerPoint PPT presentation

Number of Views:230
Avg rating:3.0/5.0
Slides: 23
Provided by: sag789
Category:

less

Transcript and Presenter's Notes

Title: El Nio Southern Oscillation ENSO


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

2
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

3
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.

4
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.

5
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.

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

7
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 0.5C, an
    El Niño event is assumed to be taking place.

8
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 -0.5C,
    an La Nina event is assumed to be taking place.

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 www.weathersa.co.za
10
Normal Conditions in the Pacific Ocean
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
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.

From www.weathersa.co.za
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 www.weathersa.co.za
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 www.weathersa.co.za
14
El Niño Conditions in the Pacific Ocean
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
15
A normal year and an El Niño year
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
16
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 http//www.wrh.noaa.gov/
17
La Niña conditions in the Pacific Ocean
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
18
Global impacts of El Niño
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
19
Global impacts of La Niña
Source http//www.wrh.noaa.gov/fgz/science/elnino
.php?wfofgz
20
El Niño facts
  • ENSO is not a weather anomaly, its 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 Niños onset does not tell us much
    about its other characteristics (e.g., intensity,
    frequency, duration).

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 , its 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.

22
Thank you for Listening!!Questions?
Write a Comment
User Comments (0)
About PowerShow.com