El Nino & La Nina
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El Niño and La Niña refer to opposite phases of the El Niño-Southern Oscillation (ENSO) cycle in the Pacific Ocean and atmosphere. El Niño occurs when warmer than average sea surface temperatures develop in the eastern tropical Pacific, while La Niña has cooler than average temperatures. These phases influence weather patterns around the world. During a strong El Niño, southern California typically sees more powerful storms and higher rainfall, while a La Niña often brings extremely dry conditions to the region.
El Nino & La Nina
- 1. El Nino and La Nina
- 2. El Nino-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
- 3. Normal conditions in the Pacific Ocean Figure 7-18a
- 4. El Nino conditions (ENSO warm phase) Figure 7-18b
- 5. La Nina conditions (ENSO cool phase; opposite of El Nino) Figure 7-18c
- 6. 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
- 7. January 1998 SST anomaly map Figure 7-19a Pg. 220
- 8. January 2000 SST anomaly map Figure 7-19b Pg. 220
- 11. El Nino/La Nina & 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)
- 12. El Nino 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
- 13. Effects of severe El Nino Figure 7-21 Pg. 222