Chapter 7 Ocean Circulation: El Ni ño. Essentials of Oceanography 7 th Edition Thurman/Trujillo. El Ni ño-Southern Oscillation (ENSO).
Chapter 7 Ocean Circulation:El Niño Essentials of Oceanography 7th Edition Thurman/Trujillo
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
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?
Normal conditions in the Pacific Ocean (pg. 218) Figure 7-18a
El Niño conditions (ENSO warm phase) (pg. 218) Figure 7-18b
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
January 1998 SST anomaly map Pg. 220 Figure 7-19a
January 2000 SST anomaly map Pg. 220 Figure 7-19b
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)
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
Effects of severe El Niños Pg. 222 Figure 7-21
El Niño visualizations • Internet site for El Niño animation • Latest SST anomaly map of the tropical Pacific
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)
End of El Niño presentation Essentials of Oceanography 7th Edition Thurman/Trujillo