1. El Niño/Southern Oscillation Major climatic perturbation on the planet Coupled atmosphere ocean process Key is the western tropical Pacific – Ascending branch of the Walker circulation – Potential energy for Kelvin wave pulse www.pmel.noaa.gov/tao/elnino/nino-home.html

2. The Southern Oscillation Discovered in 1928 by Sir Gilbert Walker Links  ’s in global climate indices Proposes a zonal circulation cell over the equatorial Pacific

3. The Southern Oscillation

4. Pressure  ’s regulate strength of the trades El Niño periods = weak trades

5. Southern Oscillation Index SOI = Tahiti - Darwin air pressure  ’s Low SOI = El Niño conditions

6. Southern Oscillation

8. Multivariate ENSO Index Combines observations of air pressure, zonal & meridional components of wind, sea surface temperature, air temperature and total cloudiness. Positive MEI = ENSO conditions

9. Walker Circulation East-to-west pressure gradients drive trades

10. Walker Circulation Vertical cell driven by warmest waters

11. Western Pacific Warm Pool

12. Coupled Walker/Ocean Circulation

14. El Niño Events Relaxation of trades causes warm pool to slosh across Pacific basin

15. El Niño Conditions

17. La Nina Opposite phase of the ENSO cycle Intensified trades & Walker circulation Thermocline undergoes maximum upwelling

18. EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued by CLIMATE PREDICTION CENTER/NCEP May 11, 2006 Synopsis: ENSO-neutral conditions are expected to prevail during the next 3-6 months. The current patterns of anomalous ocean temperatures are consistent in indicating a return to ENSO-neutral conditions in the tropical Pacific. During April SSTs were close to average at most locations between Indonesia and 90ºW (Fig. 1), which is reflected in the near zero departures observed in all of the Niño regions, except for Niño 1+2 (Fig. 2). During the month, negative SST departures developed in the extreme eastern equatorial Pacific, which is a reversal from conditions observed during February-March.Fig. 1Fig. 2

19. Today…

22. Altimetry & ENSO States Most “action” is in the tropical Pacific Effects are seen in other places – East subtropics – Western NECC region

23. Effects of an El Niño Region of ascending air has moved to center of equatorial Pacific Climate system shifts over 10,000 km to east Affects the entire planet

24. An El Niño History late 1800s Fishermen name El Niño to the periodic warm waters that appear off the coasts of Peru and Ecuador around Christmas. 1928 Gilbert Walker describes the Southern Oscillation. 1957 A large El Niño is observed which affects not just the coasts of Peru and Ecuador but the entire Pacific Ocean. 1969 Jacob Bjerknes links the Southern Oscillation with El Niño events.

25. An El Niño History 1975 Wyrtki uses island sea level to show how eastward flow causes SST’s to rise in east Pacific. 1976 An idealized computer model demonstrates that winds over the far western Pacific can change SST off Peru. 1982 A severe El Niño develops unexpectedly, but is recorded in detail with newly developed ocean buoys. 1985 Several nations launch the Tropical Ocean- Global Atmosphere (TOGA) program.

26. An El Niño History 1986 First coupled model of ocean & atmosphere predicts El Niño event. 1988 Researchers explain how the "memory" of the ocean--the lag between a change in the winds and the response of the ocean--influences terminations of El Niño and the onset of La Niña. 1996-1997 The array of instruments monitoring the Pacific, plus coupled ocean-atmosphere models, enable scientists to warn the public of an impending El Niño event.

27. Effects of an El Niño Places that were wet are now dry and vice versa

28. Effects of an El Niño

29. El Niño in Australia

31. Teleconnections Discovered in 1928 by Sir Gilbert Walker Links  ’s in global climate indices Proposes a zonal circulation cell over the equatorial Pacific

32. El Niño Hadley cells intensify as source of heat is now in central equatorial Pacific Jet stream intensifies & takes south path

33. El Niño in the United States

37. El Niño & Hurricane Damage

39. El Niño & Diseases

40. Delayed Oscillator Theory Seeds of El Nino destruction as it starts...

41. Delayed Oscillator Theory

43. El Niño Conditions

44. 97-98 El Niño Event

45. 97/98 El Niño At its peak, the 97/98 El Niño was biggest of all time

46. 97/98 El Niño

48. TOPEX/Poseidon sea level anomaly - December 1, 1997

49. 97/98 El Niño

50. OLR = outgoing longwave energy (high OLR = no clouds) 97/98 El Niño

52. More readings NOAA ENSO Page www.pmel.noaa.gov/tao/elnino/nino-home.html Review of 97/98 El Nino www.icess.ucsb.edu/~davey/Geog163/950.pdf