El Niño/Southern Oscillation

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 D’s in global climate indices • Proposes a zonal circulation cell over the equatorial Pacific

3. The Southern Oscillation

4. The Southern Oscillation • Pressure D’s regulate strength of the trades • El Niño periods = weak trades

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

6. Southern Oscillation Index

7. Southern Oscillation

8. Walker Circulation • East-to-west pressure gradients drive trades

9. Walker Circulation • Vertical cell driven by warmest waters

10. Western Pacific Warm Pool

11. Coupled Walker/Ocean Circulation

12. TOGA-TAO Array • Equatorial array of buoys (also Atlantic & Indian) • U.S., Japan, India, French, etc. partnership • http://www.pmel.noaa.gov/tao/

13. Moorings • Measure met & ocean properties • Thermocline focus • Real-time data transmission • Used in weather & climate forecasts

14. TAO Moorings

15. TAO Moorings

16. Southern Oscillation

17. El Niño Conditions

18. El NiñoEvents • Relaxation of trades causes warm pool to slosh across Pacific basin

19. El Niño Conditions

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

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

22. Equatorial Kelvin Waves • Satellite altimetry from TOPEX/Poseidon • Scenes are 10 days apart

23. Equatorial Kelvin & Rossby Waves

24. Off-Equatorial Rossby Waves Equatorial Kelvin Waves

25. Planetary Waves & El Niños

26. 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

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

28. Effects of an El Niño

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

30. El Niño & Hurricane Damage

31. El Niño & Diseases

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

34. El Niño in the United States

35. El Niño in the United States

36. El Niño in California

37. El Niño in California

38. El Niño in California

39. 97/98 El Niño • At its peak, the 97/98 El Niño was biggest of all time

40. 97/98 El Niño

41. 97/98 El Niño

42. 97/98 El Niño • TOPEX/Poseidon sea level anomaly - December 1, 1997

43. 97/98 El Niño

44. 97/98 El Niño OLR = outgoing longwave energy (high OLR = no clouds)

45. 97/98 El Niño

46. Present Conditions

47. Present Conditions EL NIÑO/SOUTHERN OSCILLATION (ENSO)DIAGNOSTIC DISCUSSION 5 January 2012 Synopsis: La Niña is expected to continue into the Northern spring 2012.

48. Present Conditions

50. Nino Regions