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“El Niño -

Southern Oscillation”Outline:Outline: What is El Nino?What is El Nino? How does it work?How does it work? What affect does El Niño What affect does El Niño

have on California?have on California?

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What is El Niño?

• El Niño is:

• El Niño occurs:

• The name, “El Niño” (means ‘boy child’ in

Spanish) as it often occurs around Christmas

time.

a warming of the equatorial eastern Pacific Ocean

about about once every 2 to 7 years

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Normal Conditions

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El Niño Conditions

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‘Normal’ conditions (sea surface temps)

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El Niño (sea surface temps)

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How does El Niño work?

El Niño is a coupled ocean-atmosphere process• It involves:

1. _____________ of the trade winds

2. __________of the eastern equatorial Pacific

3. _______ movement of the heavy rain region

4. _________ pressure in the west and reduced pressure in the east

WeakeningWeakening

WarmingWarmingEastwardEastwardIncreasedIncreased

Normal conditions:

warm water and rain in the west Pacific

El Niño conditions: warm water and rain in the central Pacific

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ENSO (El Niño-Southern Oscillation)

• The Southern Oscillation:– is the part of El Niño

– The Southern Oscillation Index is the pressure difference between Tahiti and Darwin,

– During El Niño, the pressure is _______ in the west and _______ in the east

– During El Nino, the Southern Oscillation Index is (positive/negative).

higherhigher

lower

atmospheric

Pressure(Tahiti) – Pressure(Darwin)

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Southern Oscillation Index

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How does El Niño affect the other parts of the globe

• http://www.usatoday.com/weather/tg/wninogrf/wninogrf.htm

• May change ‘normal’ storm tracks

• i.e. – Warmer and drier in pacific northwest– Wetter in California– Wetter over Southern States

• Some areas flood, other areas have drought

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m

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El Niño

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El Niño…

• …is an important modifier of local climates

• …may change global wind patterns

• …can cause floods or drought

• …is NOT a storm!!!

• …is pretty fascinating!!!