Transcript Understanding Our Environment

El Nino
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Why Does It Rain ?
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Water vapor condenses,releasing latent heat
causes air to rise, cool, and lose more water
vapor.
 Rising, expanding air creates an area of
relatively high pressure at the top .
 Air flows out of high-pressure zone
towards areas of low-pressure.
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El Nino
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La Nina, El Nino or the Southern oscillation:
A pool of warm surface water most of the
years is held by the equatorial trade wind
between Indonesia and the South America
and moves this current westwards towards
Indonesia.
Every 3-5 years the low-pressure system
breaks in Indonesia.
This giant pool of warm water moves
backward and forward between Indonesia
and S. America, this effect is called EL Nino.
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El Nino Southern Oscillation
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Large pool of warm surface water in Pacific
Ocean moves back and forth between
Indonesia and South America.
 Most years, the pool is held in western
Pacific by steady equatorial trade winds.
 Every three-five years the Indonesian low
pressure system collapses and the mass
of warm surface water surges back east.
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El Nino Southern Oscillation
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During an El Nino year, the northern jet stream
(normally over Canada) pulls moist air from the
Pacific over the U.S.This is accompanied by
intense storms and heavy rains (from California
across the midwest States).
The counterpart to El Nino is La Nina when the
eastern tropical Pacific cools down.
During intervening La Nina years, hot, dry
weather is often present (California to midwest)
Together these cycles are called El Nino
Southern Oscillation (ENSO)
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El Nino Southern Oscillation
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