el niño & la niña. three circulations of the oceans normal circulation (walker circulation) el...
TRANSCRIPT
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
• 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
First signs of El Niño
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 StudyEl 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 StudyEL 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)