Chapter 7 Ocean Circulation: El Niсo

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Chapter 7 Ocean CirculationEl Niño

• Essentials of Oceanography
• 7th Edition
• Thurman/Trujillo

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El Niño-Southern Oscillation (ENSO)

• El Niño (Spanish for the Child in reference to
  baby Jesus) warm surface current in equatorial
  eastern Pacific that occurs periodically around
  Christmastime
• Southern Oscillation change in atmospheric
  pressure over Pacific Ocean accompanying El Niño
• ENSO describes a combined oceanic-atmospheric
  disturbance

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Questions about El Niño

• What does an El Niño have to do with the price of
  eggs?
• What is La Niña?
• What kind of weather does El Niño bring to
  southern California?
• Is this an El Niño year?

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Normal conditions in the Pacific Ocean (pg. 218)
Figure 7-18a
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El Niño conditions (ENSO warm phase) (pg. 218)
Figure 7-18b
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La Niña conditions (ENSO cool phase opposite of
El Niño)
Figure 7-18c
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Anomaly maps

• Anomaly (a without, nomos law) maps show the
  difference from normal conditions
• Sea Surface Temperature (SST) anomaly maps are
  useful for identifying unusually warm or cool
  water
• Positive SST anomaly values water warmer than
  normal
• Negative SST anomaly values water cooler than
  normal

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January 1998 SST anomaly map
Pg. 220
Figure 7-19a
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January 2000 SST anomaly map
Pg. 220
Figure 7-19b
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Offshore California SST anomaly mapJanuary 1998


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Offshore California SST anomaly mapJanuary
1999(1 year later)


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El Niño/La Niña weather in southern California

• Typical weather during El Niño?
• Strong El Niños Lots of powerful storms (good
  waves), lots of rain (1997-1998 more than
  double our normal rainfall), but not always
• Moderate/Weak El Niños can have drought
  conditions or lots of rain or no effect at all
• Typical weather during La Niña?
• Extremely dry conditions (2000-2001 1/3 normal
  rainfall)

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El Niño recurrence interval

• Typical recurrence interval for El Niños 2-12
  years
• Pacific has alternated between El Niño and La
  Niña events since 1950

Figure 7-20
Pg. 221
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Effects of severe El Niños
Pg. 222
Figure 7-21
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El Niño visualizations

• Internet site for El Niño animation
• Latest SST anomaly map of the tropical Pacific

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Forecast SST anomalies Can we expect another El
Niño year?

• 9-month forecast of tropical Pacific SST
  anomalies
• Alternate link for 9-month forecast of tropical
  Pacific SST anomalies (from Palomar Oceanography
  Home Page)

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End of El Niño presentation

• Essentials of Oceanography
• 7th Edition
• Thurman/Trujillo