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E l N ino- S outhern O scillation ENSO

E l N ino- S outhern O scillation ENSO. Richard H. Grumm and Paul Knight V_2.2 10 February 2004 26March 2002. Introduction . ENSO is flow regime over the Pacific basin hinged on the distribution of sea surface temperatures

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E l N ino- S outhern O scillation ENSO

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  1. El Nino-Southern OscillationENSO Richard H. Grumm and Paul Knight V_2.2 10 February 2004 26March 2002

  2. Introduction • ENSO is flow regime over the Pacific basin hinged on the distribution of sea surface temperatures • There are two phases the warm and cold phase and a third neutral phase • The warm and cold phases get most peopled attention • ENSO affects the Walker Circulation which • Teleconnects to weather elsewhere

  3. Two Phases:El Nino/La Nina • ANOMOLOUS POOL OF WARM WATER APPEARS ACROSS THE TROPICAL CENTRAL/EASTERN PACIFIC • ANOMOLOUS POOL OF COOL WATER APPEARS ACROSS THE TROPICAL CENTRAL/EASTERN PACIFIC

  4. The well known El Nino Teleconnectionthe temporal fluctuation about globe associated with El Nino

  5. How El Nino Teleconnects Walker Circulation impacts

  6. TROPICAL PACIFIC TEMPERATURE REGIMESbut temperature anomalies tell the real story…. N E U T R A L E L N I N O L A N I N A

  7. TROPICAL PACIFIC TEMPERATURE ANOMALIESdesribe ENSO phases N E U T R A L E L N I N O 160E 180 160W 140W 120W 100W L A N I N A

  8. The SOUTHERN OSCILLATION PRESSURE DIFFERENCES BETWEEN DARWIN AND TAHITI T D Initially related to weather patterns in Australia and India.by Sir Herbert Walker

  9. SOUTHERN OSCILLATION EL NINO T D PRESSURE DIFFERENCE ? <0

  10. SOI- SOUTHERN OSCILLATION INDEX LA NINA T D PRESSURE DIFFERENCE ? >0

  11. SST ANOMALIES/ SOI INDEX WHAT IS THE RELATIONSHIP HERE ??

  12. El Nino-Warm phase of ENSO • What causes an El Nino to occur? • Trade winds in C/W Pacific weaken ->> (why?) Kelvin/Rossby wave theory • Warm water “sloshes” back eastward • Warm water appears in eastern tropical Pacific since upwelling weakens

  13. El Nino-Warm phase of ENSO • Tropical Oceanic effects of El Nino: • Positive SST anomalies of 2-6 C occur from 180 degrees to South America coast (80W) • Small negative SST anomalies in far western Pacific • Fishing industry

  14. Cooler WARMER D T Implies higher pressure at cooler Darwin than warmer Tahiti OCEANIC TEMPERATURE CHANGES DURING EL NINO

  15. El Nino-Warm phase of ENSO • Atmospheric effects of El Nino: • TROPICAL LATITUDES • SHIFTS the WALKER CIRCULATION

  16. WALKER CIRCULATION • - SFC LOW PRS ANOMALY OVER E/C PACIFIC • - SFC HIGH PRS ANOMALY OVER FAR WEST PACIFIC • - ENHANCES CONVECTION OVER CENTRAL AND EASTERN PACIFIC • - SUPRESSES CONVECTION OVER FAR WESTERN PACIFIC

  17. El Nino- Mid-latitude impacts • STRENGTHENS SOUTHERN JET STREAM ACROSS CENTRAL/EASTERN PACIFIC • Impacts North America • No well documented impacts in Europe

  18. Seasonably cool Enhances southern branch of jet stream X X Unusually warm El Nino- warm phase of ENSO

  19. El Nino- warm phase of ENSO

  20. El Nino- The warm phase of SO • Typically lasts 12-18 months • Occurs irregularly at intervals of 2 to 7 years • Sometimes is followed by La Nina • Greatest atmospheric impacts are noted near the anomalies • Some mid-latitude impacts in North American and eastern Asia

  21. La Nina- The cold phase of ENSO • What causes an La Nina to occur? • Good question! • El Nino is a rife with negative feedbacks that allow for a return to Neutral and/or La Nina regimes?

  22. La Nina- The cold phase of ENSO • Tropical Oceanic effects of La Nina: • Negative SST anomalies of 1-4 C occur from 180 degrees to South America coast (80W) • Small positive SST anomalies in far western Pacific • Fishing industry

  23. D T OCEANIC TEMPERATURE CHANGES DURING LA NINA

  24. La Nina- The cold phase of ENSO • Atmospheric effects of La Nina: • TROPICAL LATITUDES • SHIFTS the WALKER CIRCULATION

  25. WALKER CIRCULATION • - Surface High pressure ANOMALY OVER east/central PACIFIC (Tahiti) • - Surface Low pressure ANOMALY OVER far western PACIFIC (Darwin) • - ENHANCES CONVECTION OVER FAR WESTERN PACIFIC • - SUPRESSES CONVECTION OVER EASTERN AND CENTRAL PACIFIC

  26. La Nina- Mid Latitude Impacts • PACIFIC JET STREAM IS MORE VARIABLE AND FARTHER NORTH • Less southern stream storms and hence Pacific storms in southern North America • More colder air into western North America

  27. Comparison

  28. La Nina- The cold phase of ENSO • Typically lasts 12-18 months • Occurs irregularly at intervals of 2 to 7 years • Sometimes is followed by El Nino • Greatest atmospheric impacts are noted near the anomalies • Recent history suggests occurring less frequently than El Ninos

  29. MEI of recent past…some El Nino’s pointed out. T,v,q,p

  30. NINO 3.4- best teleconnection region 4 3 2 1 NIÑO SST regions 140W

  31. RECENT EL NINO/ LA NINA

  32. Evolution SST and AnomaliesNov 03-Feb 04

  33. Nina region SST Anomalies Mar 2003-Jan 2004http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory

  34. SO values Feb 2003-Feb 2004

  35. EL NINO & US PRECIPITATION

  36. EL NINO & US TEMPERATURES

  37. LA NINA-TEMP

  38. LA NINA & US PRECIPITATION

  39. Recent Events Impact • 1972-73 El Niño Event • Was big but not a record, but global food problems occurred, • Russian wheat crisis brought El Niño to fore-front • US wheat to Russia and we grew too much soy…a replacement food for anchoveta • Connections of bad weather and teleconnections to El Niño grows • 1982-83 Event: The big anomaly • thought to have been the El Niño of the Century until 1998 • big global impacts on food and weather • floods and droughts in tropics blamed on El Niño • flooding in Peru • droughts in Indonesia, Australia, north and south Africa • eastern US warmest winter in 25 years • value of long-lead forecasting grew in importance

  40. More El Niños • 1986-87 First successful El Niño Forecast • 1990-95 A long El Nino Event • a long slow El Niño • forecasts of its break-down were poor and wrong • may be one of the longest events document • was not an intense event • showed up consistent in NIÑO3.4 data • SOI was not as good an indicator (see P115 of Glantz) • 1997-98 El Nino: • the strongest on record in terms of amplitude • broke the 1982-83 events intensity • followed closely by a strong La Niña • was forecast but not as well as you might think!

  41. Conclusions • ENSO is a circulation related to both the atmosphere and the oceans • ENSO has has 3 phases • Warm- El Niño • Cold - La Niña • Neutral • These phases impact Walker Circulation • this impacts global circulation patterns, which • teleconnect to climate anomalies around the world

  42. Conclusions-II • Today, better monitored with SST data • Niño3 • Niño4 • and now the better NIÑO3.4 area • Coupled Ocean Models predictions • Forecasters should know general impacts • Consider interaction in North America of ENSO and NAO.

  43. MEI Components • sea-level pressure (P), zonal (U) and meridional (V) components of the surface wind, sea surface temperature (S), surface air temperature (A), and total cloudiness fraction of the sky (C).

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