Today

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Objectives

• learn how El Niño and La Niña work
• emphasize that the ocean atmosphere are
  strongly coupled
• understand that one component of the Earths
  system can have drastic effects on the rest of
  the Earth

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El Niño The Enigma

• Unusual oceanic and atmospheric phenomenon - an
  anomaly
• We dont know everything about it
• We cant really predict it yet

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El Niño The Term

• First discovered in 1795
• Recognized by local fisherman along Ecuador and
  Peru
• Warm, surface countercurrent
• North--gtSouth
• Discovered around Christmas-time
• The Christ Child

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El Niño Characteristics

• Normally develops in W. tropical Pacific
• Often results in natural disasters
• Occurs every 2 to 10 years
• Most recent and severe events in 1953, 57-58,
  65, 72-73, 76-77, 82-83, 91-92, 97-98,
  02-04, 06-07, 0910

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Slides from 1982-83 El Niño
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• INDEX
• Air temperature
• Sea surface temp
• Surface winds
• Cloudiness of sky
• Sea level pressure

-09-10
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Pressure!!
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Suppressed Sea Surface
Elevated Sea Surface
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Southern Oscillation (SO)

• Tradewinds weaken or fail
• Tropical winds reverse and go east instead of
  west
• Atmospheric pressure cells reverse
• Wet areas become dry (drought)
• Dry areas get flooded
• oscillates like a giant sea-saw, taking 3-5
  months

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Non El Niño
El Niño
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Coupled Ocean-Atmosphere Circulation
Non El Niño
El Niño
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Oceans Response to the SO

• Warm water moves to the east
• Elevates sea surface temperatures (SSTs) in SE
  Pacific
• Shuts down upwelling, can induce downwelling
• Reduces available nutrients
• Kills fish and sea birds - especially bad off Peru

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Non El Niño
El Niño
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Animations
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Ocean AND Atmosphere

• El Niño is both an oceanic and an atmospheric
  phenomenon
• Often called ENSO
• Scientists knew of SO from wind and precip. data
• Scientists knew of El Niño from SST data
• Didnt make connection until 1969

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Jacob Bjerknes

• Jacob Bjerknes, a Norwegian meteorologist made
  breakthrough in 1969
• Combined wind, rain, AND SST data
• Ocean atm. part of big climate engine
• Effects of ENSO not just local to Peru but could
  affect whole Pacific, whole world

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Interdisciplinarity Rules!

• Bjerknes was a meterologist who was willing to
  take a good, hard look at oceanographic data
• Oceanography a versatile science

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How Do We Track El Niño Today?

• in situ (on site) measurements
• Satellite sea surface temperature
• Computer models

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Autonomous Temperature Line Acquisition System
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Tropical Ocn Global Atm
Tropical Atm-Ocn
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La Niña

• NOT tied to the Southern Oscillation
• Tradewinds get stronger
• SSTs are lowered in SE Pacific
• Normal conditions are exaggerated
• Dry areas get drier (drought)
• Wet areas get wetter (floods)
• Occurs in between El Niños

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• INDEX
• Air temperature
• Sea surface temp
• Surface winds
• Cloudiness of sky
• Sea level pressure

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El Niño AND La Niña

• Both an ocean/atmosphere phenomenon
• Both affect wind, rain, and SST
• Both occur in cycles

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More Animations
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El Niño VERSUS La Niña

• No oscillation
• Tradewinds increase
• No reverse flow
• Decreased SST
• Upwelling increased
• Fish thrive
• Dry areas get drier
• Wet areas flood

• Southern Oscillation
• Tradewinds fail
• Reverse flow of air
• Elevated SST
• Upwelling decreased
• Fish die
• Dry areas flood
• Wet areas dry up

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Lesson to be Learned

• Earth phenomena are very much interrelated
• Ocean lt----gt Atmosphere
• Bjerknes concept of teleconnections
• We must understand in order to predict
• Invest in soybean futures after an El Niño!
• No fish meal for cattle, farmers will use soy

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Were dealing with the interplay between two very
different fluids - atmosphere and ocean - in the
boundless dimensions of time and space. ...
Abnormality in one causes abnormality in the
other.... Events such as El Niños have no
definite starting point and no end. Its a matter
of where you break into the scene, and where you
leave it. Perhaps the only thing more complex is
human behavior itself.
-- Dr. Jerome Namias, Scripps Institution of
Oceanography