Transcript el nia o by igor

El Niño
&
La Niña
THREE CIRCULATIONS OF
THE OCEANS
• Normal circulation (Walker circulation)
• El Nino circulation
• La Nina circulation
Normal conditions (Walker
conditions)
• From Polar region, Peruvian current is circulating from
eastern Pacific towards western Pacific. Strong trade
winds are taking warm surface water towards west
(ocean heats up to 28°C) while on the east upwelling
occurs (raising of colder water what results with rich
nutients for the fisheries)
• Approaching to Australia and Indonesia, the air warms
up due to high evaporation rate. This creates clouds and
results with high precipitation (the proof > rainforests).
• The overall result are floods around eastern coast of
Australia and Indonesia while on the other side, the
drught occur (Atacama desert)
Normal Circulation
El Niño circulation
• Trade winds weaken and turn the direction
• Blowing from western Pacific towards eastern Pacific,
now the warm ocean surface water approaches coast of
Peru where, after high evaporation, heavy rainfall occurs
• This results with raise in sea level and couses floods
>no upwelling > no rich nutrients > no fisheries
• On eastern side of Australia, high pressure and dense
clouds result with cold air
• The consequences are drughts and fires in the
rainforests
El Nino Circulation
Comparing two conditions
• Normal condition
El Niño condition
First signs of El Niño
• Raise in air pressure over the Indian ocean, Indonesia
and Australia
• Fall in air pressure over Tahiti, central and eastern
Pacific ocean
• Weak trade winds heading east
• Rising warm air in Peru causing rain in the deserts
• Spreading of warm water from west Pacific and the
Indian ocean to the east Pacific
>> the cause is the rain in dry areas and drought in
wet areas
Wider effects of El Niño condition
• AFFECTING THE CLIMATE
> storms, winds, floods and droughts
• Affecting plants and animals
• Economy > Fisheries
> Diseases
• Relation with hurricanes
• Increasing bush fires and worsening haze
• Decreasing air quality
• Relation to Global Warming ?
• Connections with La Nina?
History of El Niño
• Occured in:
> 1790-93
> 1828
> 1876-78
> 1891
> 1925-26
recently:
> 1986-87
> 1991-92
> 1993, 1994, 1997-98, 2002-03, 2004-05, 2006-07
Case Study
El Nino 1982. – 1983.
-caused by broad expanse of water and heavy precipitation
- raise in the surface of 11 feet
• Consequences:
• Around Peruvian coast
>2000 deaths
>losses of 13 billion $
• In Australia,Indonesia and Africa
>droughts, dust storms and forest fires
• In United States
>sharks attack due to wet and warm spring
Case Study
EL Nino 1997. – 1998.
-sea-surface temperature exceeding 28°C
-rainfall in December 1997 and January 1998 reached 15
times the average
- Consequences:
Drought over Indonesia and Papua New Guinea
>4.4 billion $ losses, famine and disease.
Ecuador and Peru
>floods and landslides, destruction of roads, houses and
crops. Losses - 3.6 billion $, cholera and malaria
Southern Africa
>loss of 50% of the wheat crop, worth $US 130 million
La Nina circulation
• La Nina is the opposite conditon of El Nino condition and
the same but stronger Normal (Walker) condition
• During La Nina, trade winds get stronger, blow in
westernly direction, bring warm ocean surface
water quicker while leaving even cooler water
along the chilean coast
• This results with floods along eastern Australia
and very dry period along western side of South
America causing fires
History of La Nina
• Tends to follow El Nino effect with some
exceptions
• Some of the strong La Nina’s:
> 1988 - 1989
> 1995
> 1999 – 2000
> 2000 – 2001 (minor exception, not expected)
> 2007
The meaning of the names
• El Nino (ENSO event – El Nino Southern
Oscillation)
• name given by South American Fishermans
> spanish for “The Christ Child”
(it came around Christmas time)
• La Nina (anti-ENSO event)
> spanish for “ The Child Girl”
(analogous to El Nino)