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

7. Nino Regions

9. 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

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

11. Walker Circulation Vertical cell driven by warmest waters

12. Western Pacific Warm Pool

13. Coupled Walker/Ocean Circulation

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

16. El Niño Conditions

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

19. EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued by CLIMATE PREDICTION CENTER/NCEP 10 May 2010 A transition from El Niño to ENSO-neutral is underway. Sea surface temperatures are decreasing across much of the Pacific Ocean. Based on current observations and dynamical model forecasts, a transition to ENSO-neutral conditions is expected by June 2010, which will continue into the Northern Hemisphere summer 2010. Although most models predict ENSO-neutral conditions, there is a growing possibility of La Niña developing during the second half of 2010.

20. Today…

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

24. 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

25. 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.

26. 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.

27. 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.

28. Coupled Walker/Ocean Circulation

29. El Niño Conditions

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

31. Effects of an El Niño

32. El Niño in Australia

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

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

36. El Niño in the United States

40. El Niño & Hurricane Damage

42. El Niño & Diseases

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

44. Delayed Oscillator Theory

46. El Niño Conditions

47. 97-98 El Niño Event

48. 97/98 El Niño At its peak, the 97/98 El Niño was biggest of all time

49. 97/98 El Niño

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

52. 97/98 El Niño

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

55. 97/98 El Niño Movie

56. 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