El Niño

• Earth rotates from west to east

• The Coriolis Effect is the influence of Earth’s rotation on air, or on any object moving on Earth’s surface.

• Objects in motion seem to be moving in a curve when they are actually moving in a straight line.

Coriolis Effect

•http://www.youtube.com/watch?v=_36MiCUS1ro

El Niño

• El Niño was first recorded in 1525 by Peruvian fishermen who noticed that the Peru current warmed up every few years. Since it often happened around Christmas, the current was called El Niño (The Christ child).

A Normal Year: Peru

• Normally the trade winds blow from east to west, pushing warm surface water into the Western Pacific and increasing the water level by 1.5 cm.

• A cold water upwelling, full of nutrients, comes up to replace the warm surface water off the Peru/Chile coast.

El Niño Year

• Every few years the trade winds slacken or even reverse (we are not sure why).

• The warm water that was piling up in the western Pacific begins to move east.

• 150 m of warm water flows across the Pacific and buries the upwelling by the Peru/Chile coast.

El Niño and Weather

• El Niño is considered to be the largest single weather influence on Earth.

• It changes the path of the jet stream, and thus affects weather everywhere.

• Normally, the jet stream is a single ‘ribbon’ of air high over North America

• During an El Niño, the jet stream splits in two, one part heading into Canada and the other section moving south into the US.

• As a result, California gets severe weather, and the southern US gets massive rainstorms.

• The Atlantic coast, including the Maritimes tends to get warmer winters and summers because the jet stream cuts off a lot of bad weather before it can migrate north.

Severe El Niños

• 1982-83: killed 2000 people and caused about 13 billion dollars in damage worldwide

• 1997-98: killed 2100 people and caused 33 billion dollars in damage. It gave us the hottest summer on record. It was also the first one to be predicted.

Predicting El Niños

• Since 1994 there have been 70 stationary buoys in the equatorial Pacific which monitor water temperature from the surface to 500 meters deep, wind direction, air temperature and relative humidity.

• Also, since 1992 a US/French satellite relays data about surface water elevation and ocean circulation.

• Computers analyze the transmitted data• This is how the 1997-98 El Niño was predicted

La Niña

• When El Niño reverses the weather patterns don’t always go back to normal; sometimes they overcompensate giving us colder than normal conditions – when this happens it is called La Niña.