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 Ni ño

Wider effects of El Ni ño 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 Ni ño Occured in: > > 1828 > > 1891 > recently: > > > 1993, 1994, , , ,

Case Study El Nino – 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 – 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 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: > > 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)