1. Where’s Winter? Explaining Seasonal Weather Variability Satellites, Weather, and Climate Module 20: Dr. Jay Shafer Mar 15, 2012 Lyndon State College 1

2. Outline Winter 2012 Rankings Possible Culprits – AO (Arctic Oscillation) – ENSO (El Nino Southern Oscillation) Climate Change Considerations 2

3. Winter 2011-2012 Stats 3

4. Temperature Anomaly: November to February 2012 Units: Degrees Celsius Persistent warm over critical cold air source regions 4

5. 5

6. Relatively dry 6

7. Burlington Oct 1 – Mar 12 Snowfall 128.41979-1980 230.51988-1989 337.72011-2012 440.11990-1991 540.41948-1949 640.71960-1961 741.31964-1965 842.42001-2002 942.91950-1951 1047.61944-1945 Records back to 1943 199.41964-1965 2105.51958-1959 3108.91955-1956 4111.41982-1983 5115.31956-1957 6118.41961-1962 7118.62011-2012 8122.11960-1961 9128.41986-1987 10128.71979-1980 Mt. Mansfield Oct 1 – Mar 12 Snowfall Records back to 1954 Snowfall Ranks 7

8. Temperature Ranks: Average Mean Temperature Nov 1- Mar 12 129.22001-2002 228.42011-2012 328.11948-1949 427.92009-2010 527.41982-1983 627.01974-1975 726.91973-1974 826.62005-2006 926.61994-1995 1026.31953-1954 130.62001-2002 229.91948-1949 329.21982-1983 428.41931-1932 528.32009-2010 628.21950-1951 727.72011-2012 827.71932-1933 927.61997-1998 1027.62005-2006 Records back to 1940 Records back to 1948 132.42001-2002 231.92011-2012 330.11948-1949 429.91982-1983 529.42009-2010 629.02005-2006 728.91994-1995 828.91990-1991 928.51953-1954 1028.51952-1953 Records back to 1894 MontpelierBurlingtonSt. Johnsbury 8

9. Seasonal Variability Burlington, VT, Seasonal Snowfall Nov 1– Mar 14 How can one explain year-to-year variations? Largest one year difference 9

10. Arctic Oscillation 10

11. Arctic Oscillation Describes high latitude pressure pattern oscillations (atmospheric oscillation) Derived from principal pattern of variability in low tropospheric (low level) atmospheric pressure patterns Most influential during winter season Can help to lock in long-lived (weeks to months) patterns that influence seasonal conditions Predictable one to two weeks ahead 11

12. Anomaly pattern associated with Arctic Oscillation (AO) Positive Arctic Oscillation State Lower heights and colder temperatures Higher heights and warmer temperature Source: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/loading.htmlhttp://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/loading.html 12

13. Surface Temperature Anomaly (Deg C) +5 to +10 days after (–) AO transitions Increased cold risk 13

14. AO Negative Phase Conditions Source: http://www.cpc.noaa.gov/research_papers/ncep_cpc_atlas/8/table_ao.html Colder temperatures Slightly wetter 14

15. AO Positive Phase Conditions Source: http://www.cpc.noaa.gov/research_papers/ncep_cpc_atlas/8/table_ao.html Warmer temperatures Drier 15

16. Blue: Winter 2011-12 Red: Winter 2010-11 AO Year-to-Year Variability 16

17. NASA: http://earthobservatory.nasa.gov/IOTD/view.php?id=77076&src=eoa-iotd What causes the AO to be positive one December and negative another? We don’t fully understand – it’s very complex! 17

18. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml Observed AO (solid line) and Forecasts (Red lines) 18

19. ENSO 19

20. EL Nino – Southern Oscillation Oceanic oscillation of equatorial sea surface temperatures (SST) in Pacific Ocean Southern Oscillation: refers to atmospheric response to oceanic fluxes of heat and moisture (oceans lead the atmosphere) Largest and most significant oscillation of SSTs in the world Has significant impacts on global circulation 20

21. Source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml 21

22. Nino 3 Region Nino 4 Region Nino 1.2 Region Temperature Anomaly (Degrees Celsius) Example La Nina (cold phase) Conditions 22

23. Source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml 23

24. Temperature Anomaly (Degrees Celsius) Example El Nino (warm phase) Conditions 24

25. Source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml 25

26. Top 10 El Niños since 1973 El Nino Winter Jet Stream Wind Anomaly Units: m s -1 Weaker Jet Stronger Jet 26

27. Top 10 La Niñas since 1970-2010 La Nina Winter Jet Stream Wind Anomaly Units: m s -1 Stronger Jet Weaker Jet 27

28. Winter 2011-12 Jet Stream Speed Anomaly Units: m s -1 Typical La Nina pattern, but note strong jet in Pac NW 28

29. La Nina this winter. Winter Mean Jet Stream Positions Red: Strong El Nino: Blue Strong La Nina Green: Winter 2011-12 29

30. Source: NOAA - http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#GLOBALimpactshttp://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#GLOBALimpacts El Nino: La Nina: 30

31. 31

32. NOAA: http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml#NVChttp://www.cpc.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml#NVC Winter Snowfall Anomalies: La Nina Conditions Below average Above average 32

33. NOAA: http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml#NVChttp://www.cpc.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml#NVC Winter Snowfall Anomalies: El Nino Conditions Below average Above average 33

34. Climate Change Signals 34

35. Winter Air Temperature Anomalies Last 10 Years Warming is occurring rapidly at high latitudes. 35

36. St. Johnsbury, VT, Average Temperature Nov 1 – Mar 14 36

37. Burlington, VT, Average Temperature Nov 1– Mar 14 37

38. Mt. Mansfield, VT, Seasonal Snowfall Nov 1– Mar 14 38

39. Burlington, VT, Seasonal Snowfall Nov 1– Mar 14 39

40. http://journals.ametsoc.org/doi/full/10.1175/2011WCAS1096.1?prevSearch=[Contrib%3A+alan+betts]&searchHistoryKeyhttp://journals.ametsoc.org/doi/full/10.1175/2011WCAS1096.1?prevSearch=[Contrib%3A+alan+betts]&searchHistoryKey= Betts 2011 40

41. Betts 2011 41

42. Activity 42

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45. Nino3.4 vs Burlington Winter Snowfall El Ninos La Ninas 3: Above 1: Below 4: Above 2: Below 45

46. Nino3.4 vs Burlington Winter Snowfall El Nino + Snow N=6 El Nino - Snow N=3 La Nina + Snow N=6 La Nina - Snow N=5 46

47. Nino3.4 vs. Burlington Winter Temperatures La Ninas 5: Above 2: Below El Ninos 4: Above 3: Below 47

48. Nino3.4 vs. Burlington Winter Temperatures El Nino Warm N=6 El Nino Cold N=4 La Nina Warm N=7 La Nina Cold N=3 48

49. ENSO Conclusions A lot of spread, ENSO does not explain much of the variability Other factors must be at play, complex interactions of tropics and high latitudes Slight tendency for snowier winters to be associated with La Ninas (top 3 winters were La Nina winters), however this year is an exception 49

50. Post Assessment Questions 50

51. Arctic Oscillation Pacific Jet Stream Patterns ENSO El Nino: Warm or positive phase of ENSO featuring well above average sea-surface temperatures in the equatorial central and eastern Pacific Ocean. La Nina: Cold or negative phase of ENSO featuring well below average sea-surface temperatures in the equatorial central and eastern Pacific Ocean. 51