Sources of Variability

1. The Climate-Weather Link and U.S. Hazards PredictionByEd O’LenicNOAA-NWS-Climate Prediction CenterIAEM 50th Anniversary Conference and ExhibitColumbus Convention Center and Hyatt Regency HotelColumbus, OhioOctober 13, 2002

2. Tropical intra-seasonal oscillations (MJO) El Nino/Southern Oscillation (ENSO) Trend, Pacific Decadal Oscillation (PDO) Time Scales of Variability Sources of Variability • Intra-Seasonal – within season • Inter-Annual – year-to-year • Decadal – decade-to-decade

3. The sun is the source of all energy in the atmosphere-ocean-land system. The pole-to-equator temperature difference, created by sunshine heating the atmosphere-ocean-land system unevenly, drives large-scale atmospheric motions. Motions act to destroy temperature differences & balance in-coming vs. out-going radiation. Tropical disturbances, e.g., El Nino, La Nina, MJO, PDO are particularly effective at changing this large-scale difference, or gradient (difference/distance). This changes the location and strength of the major jet streams, which affects the weather. Temperature gradients also cause disturbances on smaller space and time scales, monsoons, cyclones, fronts, squall-lines, thunderstorms, clouds, etc… The oceanic circulation is important, too, but that’s a whole other lecture. Solar radiation => Temperature gradients => Motions

4. Climate Versus Weather Top Graph: Observed daily average Temperature (T), May 2000-April 2001 (jagged curve, an example of “weather”), and 30-year average (1971-2000) of daily average T (also called the “normal”, (smooth curve) the standard definition of “climate”) at Albany, New York. Note the large day-to-day variability indicated by the red (above-normal) and blue (below normal) daily T events. Bottom Graph: Result of subtracting the normal from the daily average T in the top graph and then performing a 31- day running average. Note the expanded scale on the lower graph. The extended periods of above and below normal 31-day average T are, examples of short-term climate variability. Green line is the average of the departures over May 2000-April 2001.

5. Storms • STORMS: REGIONS OF DISTURBED WEATHER – CLOUDS, PRECIPITATION, STRONG WINDS ASSOCIATED WITH EITHER: • LARGE-AMPLITUDE HORIZONTAL TEMPERATURE GRADIENTS IN MIDDLE LATITUDES (CYCLONES), • OR • OCEAN SURFACE TEMPERATURES EXCEEDING • 26 ½0 C AND WEAK LARGE-SCALE VERTICAL WIND SHEAR IN THE TROPICS AND SUB-TROPICS (TROPICAL STORMS).

6. Coastal Population Rising The population in regions subject to strong coastal storms is rising rapidly. Many of these people have little or no know- ledge of the potential for disaster in these areas.

7. Hurricanes and winter storms rank among the most expensive U.S. disasters Insured Losses of U.S. Disasters, 1950-94

8. The Great Snow and Wind Storm of Thanksgiving, 1950 Unnamed wind storm: November 23-December 2, 1950. An intense, slow-moving extra-tropical storm along the U.S. East Coast was accompanied by sustained gale-force winds for several days, wind gusts to hurricane-force (including a gust to 110 mph on a sky scraper in New York City), wind-driven flooding near the coast (including 12 feet of flood water at La Guardia Airport), heavy snow in Western Pennsylvania. East Coast and Great Lakes shipping was severely impacted. Record low temperatures were observed in the South, including 3 degrees F at Atlanta, Georgia. The insured loss from the storm was ~$6-7 B (in recent dollars).

9. U.S. Hazards Assessment Temperature/Wind Precipitation U.S. Hazards Assessmenthttp://www.cpc.ncep.noaa.gov/products/predictions/threats Soil/Wildfire Composite

10. U.S. Hazards Assessmenthttp://www.cpc.ncep.noaa.gov/products/predictions/threats A Hazards conference call is held each Wednesday at 2PM Eastern Time. • Hazards Briefing Sequence • Satellite/Radar • IR Anim: Global, North America • Water Vapor Anim • US Radar • Climate Monitoring • SST Anim: Glbl, Pac, Atl/E Pac • 7d SST: Pac, Atl/E Pac • EQPAC T-Depth Plot • EQPAC T-Depth Anim: Wk, Mon • Obs P: 1/7d, 30d, 90d • ENSO Bull: Text, Fig 1, Fig 2 • Sea Level Anim • Z Loops: NH, Globe • CDC OLR Anom • Cities Temp • Cities Precip • Forecasts • NCEP Ensembles • NCEP Global Modeling Branch • CPC D+8 and Week 2 Forecasts • Long Range: Mon, Seas • Medium Range: 6-10 Day, 8-14 Day • Ensemble Spaghetti Charts • 3-5 Day Prcp Prbs • 3-5 Day Temp Fcst • Heat Index • Blocking: Obs & Fcsts • Predictability • Indices

11. Linkage between weather and climate Jet streams, tropical storms, Extreme events, floods, diurnal cycle, … Weather Reacts to changes in heat budget, temperature gradient. Reacts to changes in heat budget through changes to planetary-scale temperature gradient, which affect weather. Reacts to changes in the global heat budget Decadal Climate Variability Short-term Climate Variability Trends of unknown origin, Trends in ENSO & AO, Global Warming, Thermohaline Circulation, Ultra-slow oscillations ENSO, MJO, PDO (tropics) AO, PNA, Storm Tracks, Droughts, …(extra-Tropics)

12. El Nino warms the global tropics, strengthening the pole-equator temperature difference. El Niño causes drought in normally wet regions and floods in normally dry regions. La Nina cools the global tropics, weakening the pole-equator temperature difference. La Niña causes floods in normally wet regions, makes dry regions drier. El Niño / Southern Oscillation - ENSO

13. El NINO/Southern Oscillation

14. El Nino Global Precipitation Impacts

15. ENSO Impacts

16. El Nino 1997-98 U.S. ENSO Impacts ENSO Impacts illustrate the basis of the climate-weather link.

17. El Nino summer: Few Atlantic Storms

18. La Nina summer: Many Atlantic Storms

19. Observed and Annual Cycle of Precipitation near SFO El Nino-related Above normal rainfall

20. The Madden-Julian Oscillation (MJO): A disturbance in tropical cloudiness, rainfall, wind and pressure • Consists of a cloudy, rainy, strong low-level westerly wind phase and a non-cloudy, dry, low-level easterly wind phase. • Move from eastward from the Indian Ocean around the globe in 30-60 days. Disturbances are ~1500 km wide. • Most active during ENSO-neutral years (especially just prior to El Niño). • Affects the frequency of extreme weather events, such as floods, in winter, and tropical cyclones and monsoons, in summer. • Low-level westerly wind bursts during cloudy phase warm the ocean, reverse easterlies, contribute to onset of El Nino.

21. Intra-Seasonal Variability of Hurricanes Intra-Seasonal Variability of HurricanesGreen~above-average cloudiness and rainfallBrown~below-average cloudiness and rainfall Madden-Julian Oscillations (MJO) – 30-60 day disturbances in tropical cloudiness

22. When the MJO maximum in tropical rainfall shifts eastward from Indonesia to the central tropical Pacific, the jet stream over the North Pacific gradually extends eastward towards the west coast of the U.S. and intensifies. This pattern favors the occurrence ofheavy precipitation events, along the Pacific Northwest coast.

23. TROPICAL CYCLONES Hurricane Floyd 2029 UT (0429 EST) Sep 14, 1999

24. U.S. Hazards Assessment

25. MAJOR REGIONS OF TROPICAL STORM ACTIVITY

26. Atlantic Tropical Storm Climatology

27. Eastern North Pacific Tropical Storm Climatology

28. Atlantic Tropical Storms, 1967-2000 Low numbers of storms does not imply weak storms Category 5 Andrew

29. Extra-Tropical Cyclones GOES water vapor 8.1 microns Feb 14, 2002

30. North Atlantic Oscillation (NAO) The North Atlantic Oscillation is the pattern most-closely associated with winter weather over North America, the Atlantic and Europe. The pattern at right shows how the pattern differs from the 30-year average. Red is for abnormally high pressure, blue is for abnormally low pressure. The pattern shown is the positive phase. The reverse pattern is the negative phase.

31. NAO Phases/Impacts

32. NAO Index, Monthly Mean, 1950-2002

33. AO-ENSO Relationships –JFM Temperature Anomaly (0C) by AO and ENSO Phase

34. Global Temperature Trends

35. IPCC Estimate of Impact of Global Warming on Storm Activity

36. Climate = average of weather but controls “statistics” of weather. This is the basis of the climate-weather link. U.S. Hazards Assessment emphasizes C-W Link. Tropical disturbances, MJO, ENSO cause much of the observed intra-seasonal to inter-annual variability in storms in low and middle latitudes. MJO is related to intense rain events in NW U.S. El Nino brings enhanced storminess and damage to the California coast. Tropical storm frequency shows large variability on decadal and longer time scales. - AO phase is related to strong U.S. winter cyclones. IPCC estimates storm strength and frequency will rise. http://www.wmo.ch/index-en.html Summary