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Flavors of Climate variability: El Nino, La Niña, Recurring Jet Stream patterns, Multi-Decadal Variability By Dr. Gerry Bell Climate Prediction Center (CPC) NOAA/National Weather Service/ National Centers for Environmental Prediction Presented to Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) 17 January 2013 www.cpc.ncep.noaa.gov Outline 1. Dinstinguishing weather and climate, climate variability 2. Climate variability linked to El Niño and La Niña (ENSO) 3. Climate variability linked to recurring jet stream patterns (Teleconnections) • Some concepts • Pacific/ North American Pattern (PNA) • North Atlantic Oscillation (NAO) • Arctic Oscillation (AO) 4. Climate variability linked to decadal ocean patterns • Atlantic Multi-Decadal Oscillation (AMO) • Pacific Decadal Oscillation (PDO) 5. Summary What is Weather? Weather: Short-term (hourly to daily) changes in temperature, humidity, precipitation, wind, etc. Weather is what the TV weatherman talks about. Examples: Thunderstorms, winter storms, hurricanes, tornadoes, a short-term flood event, cold/warm fronts, a sunny or rainy day, etc. Thunderstorm Snowstorm www.squidoo.com/thunderstormpictures. A weather forecast showing predicted fronts and rainfall. Hurricane Katrina www.accuweather.com. Another daily weather forecast. Climate, Climate Variability, and Climate Change Climate: Average or slowly varying aspects of atmosphere-ocean system. (e.g., Annual mean conditions, the four seasons, monsoons, hurricane season, average temperature changes throughout the year, day-night temperature cycle, etc.) Example Daily Temperatures Weather: Daily temperatures Climate: 30-year average daily temperature Climate Variability: A cool summer Climate Variability: Variations in the average state of the climate due to natural processes (recurring patterns of ocean temperature, tropical rainfall, jet stream winds, etc.). Climate Change: Variations in either the mean state of the climate or in its variability, which is attributed directly or indirectly to human activity (global warming due to increasing CO2 concentrations) Climate Variability •Climate variability typically occurs over vast distances (continental, hemispheric, global), with time scales ranging from weeks to years to decades. •Climate variability is often linked to recurring jet stream, ocean temperature, and tropical rainfall patterns. •Climate variability differs throughout the world and with the seasons. Some examples of climate variability: Index of Atlantic Ocean Temperature Departures Atlantic Multi-Decadal Oscillation El Niño Sea surface temperature Departures Atlantic Hurricane Season Strength El Niño Impacts African Sahel Drought 2009-2010 Record Snowfall Climate Variability Linked to El Niño and La Niña (ENSO) El Niño and La Niña •El Niño and La Niña represent extremes in the El Niño/ Southern Oscillation (ENSO), a leading source of year-to-year climate variability. •Discovered in stages: Peruvian fisherman, Sir Gilbert Walker (1920’s), Jacob Bjerknes (1960’s). •Related to changes in tropical Pacific Ocean temperatures; Occur roughly every 3-5 years, typically last 9-12 months. •El Niño: a warming of the central and eastern equatorial Pacific •La Niña: a cooling of the central and eastern equatorial Pacific •NOAA classifies El Niño and La Niña episodes using the Oceanic Niño Index (ONI). •ONI=3-month running mean of SST departures in the Niño 3.4 region (east-central equatorial Pacific) Monitoring and Predicting El Niño and La Niña (ENSO) www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml U.S. Impacts by Season Temperature Precipitation Snow U.S. Temperature and Precipitation Distributions Weekly ENSO Evolution, Status, and Prediction Presentation Monthly EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION El Niño/ La Niña Tutorial http://www.cpc.ncep.noaa.gov/product s/analysis_monitoring/ensocycle/enso _cycle.shtml Recent Model Forecasts Official ENSO Probability Forecast Normal Ocean Surface Temperatures (°C) January Equator Warm, Wet Cool, Dry Date Line ˚C Equatorial Cold Tongue Equatorial ocean temperatures are normally warmest in the western Pacific and coolest in the eastern Pacific. Tropical rainfall is normally strongest in the Western Pacific/ Indonesia region, and non-existent over the equatorial cold tongue. January Ocean Temperatures (oC) Comparing Normal to El Niño Normal Temperatures El Niño Temperature Departures •El Niño: a warming of the central and eastern equatorial Pacific January Ocean Temperatures (oC) Comparing Normal to La Niña Normal Temperatures La Niña Temperature Departures •La Niña: a cooling of the central and eastern equatorial Pacific Wintertime Tropical Rainfall (Inches) Strong La Nina Strong El Nino Pacific Jet Stream Pacific Jet Stream Normal Jet Normal Jet Drier Wetter Wetter Drier Scales show Inches of Rain 4 8 12 16 20 El Niño Deep tropical convection and Pacific jet stream extend across the central and eastern Pacific. 4 8 12 16 20 La Niña Deep tropical convection and Pacific jet stream retracted westward toward Asia. •El Niño and La Niña produce massive re-distributions of rainfall across the tropical Pacific Ocean. •This subsequently alters the Pacific jet stream, resulting in mid-latitude climate variability across the North Pacific Ocean and North America. Global El Niño Temperature and Precipitation Impacts DecemberMarch Mid-latitude impacts stronger in winter hemisphere June-August El Niño impacts include: • Temperature and precipitation patterns • Jet streams and storm tracks • Monsoons and hurricanes Global La Niña Temperature and Precipitation Impacts DecemberMarch Mid-latitude impacts stronger in winter hemisphere June-August La Niña impacts include: • Temperature and precipitation patterns • Jet streams and storm tracks • Monsoons and hurricanes El Niño Winter Impacts: North Pacific and North America El Niño: Persistent, extended Pacific jet stream and amplified storm track •The Pacific jet stream is directly influenced by tropical convection patterns. •El Niño strengthens and extends this jet stream and its storm track eastward, •Affects winter weather across the North Pacific Ocean and North America. 7 La Niña Winter Impacts: North Pacific and North America La Niña: Weaker and Variable Pacific Jet Stream •La Niña weakens the Pacific jet stream and makes it much more variable, often shifting it back toward Asia. •The polar jet steam is also shifted westward. •Affects winter weather across the North Pacific Ocean and North America. 8 El Niño and La Niña Hurricane Season Impacts More Less Less More No Change Less More More Less No Change Less More More= More hurricanes Less= Fewer hurricanes Red text refers to El Niño signal. Blue text refers to La Niña signal. 11 Climate Variability Linked to Recurring Jet Stream Patterns (Teleconnections) Recurring Jet Stream Patterns Another Important Source of Climate Variability •Jet streams (rivers of strong winds at about 35,000 ft altitude) are associated with very large patterns of air pressure, wind, storminess, precipitation, and temperature. •Much climate variability is linked to recurring jet stream patterns, which influence air pressure, wind, temperature, and precipitation patterns across vast distances (across ocean basins, across a continent, etc.). These inter-related patterns are called Teleconnections. El Niño Impacts El Niño and La Niña produce teleconnections across the America’s. Air Pressure Patterns Air Pressure and Wind Relationships Winds flow clockwise around areas of High Pressure Winds flow counter-clockwise around areas of Low Pressure H L Air Pressure, Temperature and Precipitation Relationships Stormier, Warm and Cold fronts Clear Weather Warmer H Colder, Drier L Warmer, Wetter Jet Streams and Air Pressure Jet Stream and Air Pressure Relationships Lines of Equal Pressure Low Pressure JetStream Core Jet High Pressure High Pressure Low Pressure Jet Streams are associated with a 4-celled pressure pattern. Changes in jet stream position and strength are associated with corresponding changes in this pressure pattern - a jet stream related teleconnection pattern. Jet Streams, Precipitation and Storms Jet Stream and Precipitation Relationships Dry Wet JetStream Core Jet Wet Dry Jet Streams produce a 4-celled pattern of wet/dry Lines of Equal Pressure Jet Stream and Storm Relationships Storms Decay Here Storms JetStream Core Form Here Jet Jet streams influence regions of storm formation/ decay Jet stream variability also produces these teleconnection patterns. Putting It All Together Jet Stream, Pressure, Temperature, Precipitation, Storm Relationships Cooler, Drier Storms Decay here Low Pressure JetStream Core Jet Wetter, Warmer High Pressure Wetter, Storms Form here Drier High Pressure Lines of Equal Pressure Low Pressure Jet stream-related patterns of air pressure, storminess, precipitation, and temperature can span vast distances. What we see as “Whacky Weather” (such as might be gleaned from this schematic), can simply be jet stream-related teleconnection patterns. Average Winter Jet Streams, Air Pressure, Storminess Lines of Equal Pressure L Jet Stream H Pacific Jet Stream H L H L H L Atlantic Jet Stream Storm Formation Region •The sheer scale of the two main jet streams is evident, along with high pressure (H) and low pressure (L) areas, and areas of storm formation. •Fluctuations in strength and location of the Pacific and Atlantic jet streams produce several teleconnection patterns that affect the North Pacific, North America, the North Atlantic, and Eurasia. We already saw some of these impacts with El Niño and La Niña. Teleconnections: Monthly Monitoring at CPC www.cpc.ncep.noaa.gov/data/teledoc/telecontents.shtml SomeTeleconnection Patterns Air Pressure Patterns Precipitation Patterns Recent Monthly Index Values Temperature Patterns Historical Time Series (1950-Pres) Teleconnections: Daily Forecasts at CPC www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml Daily Indices and Forecasts Average Winter Jet Streams, Air Pressure, Storminess Lines of Constant Pressure L Jet Stream H Pacific Jet Stream H L H L H L Atlantic Jet Stream Storm Formation Region Pacific/ North American (PNA) Pattern Related to changes in position and strength of the Pacific jet stream. January Jet Stream and Air Pressure Departures Positive Phase of PNA Pattern Pacific Jet Stream Negative Phase of PNA Pattern Pacific Jet Stream Higher pressure Pacific Jet Stream Pacific jet stream and region of storm formation shift eastward to western U.S. (as during El Niño) Lower pressure Storm Formation Region Pacific jet stream and region of storm formation shifts westward toward Asia (as during La Niña). The PNA pattern produces climate variability across the North Pacific Ocean and North America. It is sometimes linked to El Niño and La Niña. Pacific/ North American (PNA) Pattern Winter vs. Summer Correlation With Surface Air Pressure •Correlation patterns reflect sign of anomalies for positive phase of PNA pattern. Higher Pressure Lower Pressure Correlation With Surface Temperature •Wintertime impacts are stronger than in summer. Warmer Colder Correlation With Precipitation Wetter Drier Pacific/ North American (PNA) Pattern Negative Phase Air Pressure Departures Higher Pressure Lower Pressure Surface Temperature Departures Warmer Colder Precipitation Departures Wetter Drier Pacific/ North American (PNA) Pattern Index Time Series: 3-Month Running Means The PNA pattern varies from weeks to months to years, and produces climate variability across the North Pacific Ocean and North America. North Atlantic Oscillation (NAO) Related to North-South Fluctuations in North Atlantic Jet Stream Wintertime NAO Index 1950-Present Cold Warm, Wet Cold, Dry Warmer, Less snow Smoothed NAO Index Back to 1860 Warm Cold, Dry Warm, Wet Colder, Snowier http://www.ldeo.columbia.edu/res/pi/NAO/ The NAO varies from weeks to years to decades, producing climate variability extending from central North America to Eurasia and Africa. North Atlantic Oscillation (NAO) Correlation With Surface Air Pressure •Correlation patterns reflect sign of anomalies for positive phase of PNA pattern. Higher Pressure Lower Pressure Correlation With Surface Temperature •Wintertime impacts are stronger than in summer. Warmer Colder Correlation With Precipitation Wetter Drier North Atlantic Oscillation (NAO): Negative Phase Surface Air Pressure Departures Higher Pressure Lower Pressure Surface Temperature Departures Warmer Colder Precipitation Departures Wetter Drier Winter El Niño – NAO Temperature Composites El Niño Only •Understanding combinations of climate signals is important. •El Niño impacts can vary depending on NAO and other climate factors (AMO, PDO). El Niño and Negative NAO •Take care when performing regression analysis on individual climate factors. El Niño and Positive NAO oC Wintertime Arctic Oscillation (AO) Contains aspects of PNA and NAO patterns Positive Phase Negative Phase Weaker Icelandic Low Stronger Icelandic Low Weaker Aleutian Low Stronger Aleutian Low Higher pressure Normal Atlantic jet stream Lower pressure AO-related Pacific and Atlantic jet stream •The AO reflects air mass exchange between polar region and middle latitudes. •AO affects Pacific and North Atlantic jet streams and storm tracks. •AO produces hemispheric-scale climate variability, with largest impacts extending from the North Pacific Ocean to Eurasia Arctic Oscillation (AO): U.S. Winter Impacts Positive AO Stronger Winds, Waves More rain, clouds More Ice, snow Less rain And clouds Frequent warm-ups Warmer Fewer Nor’easters More heavy rain events Negative AO Colder More Nor’easters More cold-air outbreaks Increased Snowfall The AO varies from weeks to years to decades, producing hemispheric climate variability. Many impacts are similar to PNA and NAO patterns. Climate Variability Linked to Decadal Ocean Patterns •Atlantic Multi-Decadal Oscillation (AMO) •Pacific Decadal Oscillation (PDO) The Atlantic Multi-Decadal Oscillation (AMO) Sea Surface Temperature Departures (oC) During June-August 1995-2011 Map depicts warm phase of AMO ˚C •Reflects changes in Atlantic Ocean temperatures occurring on time scales of 25-40 years. •Discovered in 1920 by Sir Gilbert Walker •Affects Indian Monsoon, west African monsoon, Atlantic hurricane activity. The Atlantic Multi-Decadal Oscillation (AMO) and Monsoon Rainfall in India and Western Africa Observed AMO Index Jun.-Sep. West Central India Rainfall Departures Jun.-Sep. African Sahel Rainfall Departures This AMO-Related Pattern Increases Atlantic Hurricane Activity for Decades at a time Warmer Warmer Wet High-activity eras for Atlantic hurricanes are associated with these conditions. Low-activity eras have opposite departures from normal. ACE index shows the overall strength of the hurricane season. Multi-decadal fluctuations in season strength are clearly evident. The Pacific Decadal Oscillation (PDO) Sea Surface Temperature Departures (Shading) Negative Phase Positive Phase Can Reinforce El Niño Can Reinforce La Niña Observed PDO Index •Reflects changes in Pacific Ocean temperatures in both the tropics and higher latitudes occurring on time scales of decades. •Discovered in 1996 by Fisheries scientist Steven Hare •Predominant source of inter-decadal climate variability across Pacific Ocean Summary Climate Variability linked to ocean temperature fluctuations • El Niño/ La Niña: Global impacts, strongest in winter hemisphere • North Atlantic: Atlantic multi-decadal oscillation (AMO). • North Pacific: Pacific Decadal Oscillation (PDO). Climate Variability linked to recurring jet stream patterns PNA, NAO, other teleconnection patterns • Seasonally dependent, continental scale, Vary months to seasons to decades (NAO). Arctic Oscillation (AO): • Combines parts of PNA and NAO • Hemispheric temperature and precipitation impacts. Combining these climate signals is very important for making seasonal predictions. Questions?