Ocean Circulation El Nio El NioSouthern Oscillation ENSO
- Slides: 16
Ocean Circulation: El Niño
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 oceanicatmospheric 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 Figure 7 -18 a
El Niño conditions (ENSO warm phase) Figure 7 -18 b
La Niña conditions (ENSO cool phase; opposite of El Niño) Figure 7 -18 c
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 Figure 7 -19 a
January 2000 SST anomaly map Figure 7 -19 b
Offshore California SST anomaly map: January 1998
Offshore California SST anomaly map: January 1999 (1 year later)
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 Figure 7 -21
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