REMINDERS: Midterm 2: Friday, February 28 - lecture material covering chapters 6, 7, and 15 (since first midterm and through Wed lecture) - same Format as first midterm UPCOMING REVIEW SESSIONS: - Thursday, Feb 27, 6:30-8:00pm in HSS 1330
Now, back to the Surface Winds... Polar Easterlies Polar Front Mid-Latitude Westerlies Horizontal Shear Zone - wind changes direction and/or speed - will induce air to rotate => Cyclonic Flow is induced here => Mid-latitude storms (low pressure) may form if conditions are right
On Monday discussed 1) Waves in Jet Stream 2) Jet Streaks and how these factors can lead to divergence aloft Divergence = more air leaving a region than entering
Clicker Question Set Frequency to "AD" Divergence of air aloft will cause the surface pressure to: (A) Decrease (B) Increase (C) No impact on surface pressure
Clicker Question Set Frequency to "AD" Divergence of air aloft will cause the surface pressure to: (A) Decrease (B) Increase (C) No impact on surface pressure
h"p://www.mesoscale.iastate.edu/agron206/anima9ons/05_cnwfronts.html
DEFINITIONS SST = Sea Surface Temperature SST Anomaly = Difference between the SST and the average SST
DEFINITIONS SST = Sea Surface Temperature SST Anomaly = Difference between the SST and the average SST Upwelling Pacific Ocean PERU
DEFINITIONS SST = Sea Surface Temperature SST Anomaly = Difference between the SST and the average SST Upwelling Tradewinds PERU 1. Prevailing winds blow offshore - away from land
DEFINITIONS SST = Sea Surface Temperature SST Anomaly = Difference between the SST and the average SST Upwelling Tradewinds PERU Current 1. Prevailing winds blow offshore - away from land 2. Wind pushes water - forms current away from land
DEFINITIONS SST = Sea Surface Temperature SST Anomaly = Difference between the SST and the average SST Upwelling Tradewinds PERU Current 1. Prevailing winds blow offshore - away from land 2. Wind pushes water - forms current away from land 3. Water near coast replaced by deep water = UPWELLING - colder and more nutrient rich
NORMALLY: SST off Peru warms a bit in December (due to changes in winds/currents)
NORMALLY: SST off Peru warms a bit in December (due to changes in winds/currents) Less upwelling: - less nutrients in water - fish feed elsewhere - economy suffers
NORMALLY: SST off Peru warms a bit in December (due to changes in winds/currents) Less upwelling: - less nutrients in water - fish feed elsewhere - economy suffers Normally lasts only a month or so ==> called El Nino ( the child ) by locals
NORMALLY: SST off Peru warms a bit in December (due to changes in winds/currents) Less upwelling: - less nutrients in water - fish feed elsewhere - economy suffers Normally lasts only a month or so ==> called El Nino ( the child ) by locals When warm SST off Peru persists for longer periods ==> Major El Nino Event
A MAJOR EL NINO EVENT IS: - A WARMING OF SST IN THE EASTERN TROPICAL PACIFIC - OCCURS PERIODICALLY --- USUALLY 3-7 YEARS APART
A MAJOR EL NINO EVENT IS: - A WARMING OF SST IN THE EASTERN TROPICAL PACIFIC - OCCURS PERIODICALLY --- USUALLY 3-7 YEARS APART - ALSO CALLED - ENSO (El Nino - Southern Oscillation) - Warm Event
EL NINO IS NOT - A FLOOD - A HURRICANE - AN INDIVIDUAL STORM - A DROUGHT
HISTORY: EARLY 1900 s - Several meteorologists observe pressure fluctuations in South Pacific ==> called Southern Oscillation
HISTORY: EARLY 1900 s - Several meteorologists observe pressure fluctuations in South Pacific ==> called Southern Oscillation 1960 s - First understood that Southern Oscillation and El Nino were related
HISTORY: EARLY 1900 s - Several meteorologists observe pressure fluctuations in South Pacific ==> called Southern Oscillation 1960 s - First understood that Southern Oscillation and El Nino were related 1980 s - Just started to understand effects of El Nino conditions on global circulation
Southern Oscillation: Usually measured using surface pressures at Darwin (D) and Tahiti (T) T D
When pressure is unusually high in Darwin, pressure is unusually low in Tahiti and vice-versa.
Southern Oscillation Index (SOI) SOI = Pressure at Tahiti - Pressure at Darwin
Eastern Pacific SST Anomalies Southern Oscillation Index (SOI)
1/2 meter 4. Warm SST 1. Tradewinds 2. Ocean Current 3. Upwelling S. America NORMAL CONDITIONS 1. Tradewinds blow east to west (easterly) 2. Wind pushes water towards west (equatorial current) 3. Upwelling results in relatively cool SST in Eastern Pacific 4. Water warms from solar energy as it moves west ==> SST increases from east to west along equator 5. Sea level higher in west ~ 1/2 meter (18 inches)
West Pacific Warm Pool SST more than 30 C ~ 86-88 F
Thermal Circulation warm cold
WHEN PRESSURE DIFFERENCE BETWEEN WEST & EAST PACIFIC DECREASES ====> TRADEWINDS SLOW (OR REVERSE) S. America 1. Kelvin Wave EL NINO CONDITIONS WATER WARMS 2. Upwelling decreases 1. Piled up water flows back toward S. America (Kelvin Wave) 2. Little or no upwelling 3. Water in East Pacific warms quickly
1998 EL NINO
Shift in Warm Water also Occurs Below Ocean Surface Normal Conditions El Nino Conditions Represents Displacement of a VERY LARGE amount of energy!!
Clicker Question Set Frequency to "AD" Over the areas with positive SST anomalies, would you expect (A) less precipitation than normal (B) more precipitation than normal (C) no change in precipitation
Clicker Question Set Frequency to "AD" Over the areas with positive SST anomalies, would you expect (A) less precipitation than normal (B) more precipitation than normal (C) no change in precipitation
LOCAL (TROPICAL PACIFIC) EFFECTS OF EL NINO EVENTS WARMER SURFACE WATER GREATER EVAPORATION INCREASED CONVECTION MORE PRECIPITATION EXPECT TO SEE MORE PRECIPITATION IN EASTERN TROPICAL PACIFIC DURING EL NINO CONDITIONS
More Precipitation in Eastern Tropical Pacific During El Nino reduced precipitation increased precipitation
NON-LOCAL EFFECTS OF EL NINO EVENTS HOW DOES THE TROPICAL SST AFFECT THE CLIMATE IN CALIFORNIA??? DISPLACEMENT OF LARGE WARM SST AREA REDISTRIBUTION OF ATMOSPHERIC HEATING IN TROPICS LEADS TO CHANGE IN HADLEY CIRCULATION AFFECTS SUBTROPICAL AND POLAR JET STREAMS In Eastern N. Pacific, jet streams intensify and are displaced from normal JET STREAMS ARE A MAJOR CONTROLLING FACTOR FOR WINTER STORMS IN U.S.
Precipitation Anomaly during La Nina =====> Precipitation Anomaly during El Nino <=====
2010: EL NINO Expected Precipitation Anomaly during El Nino <===== Precipitation Anomaly at this time in 2010 Oct 1 2009 - Feb 22 2010 =====>
2012: LA NINA Expected Precipitation Anomaly during La Nina <===== Precipitation Anomaly so far this year Oct 1 2011 - Feb 24 2012 =====>
WHAT S GOING ON CURRENTLY?
Last 20 Years Nino 3.4 Region of Central Tropical Pacific Last 12 Months http://www.cpc.ncep.noaa.gov/data/indices/ Degree C http://www.cpc.ncep.noaa.gov/
http://www.esrl.noaa.gov/psd/map/clim/sst.shtml
Actual Temps Anomalies http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/
Recent Evolution of Equatorial Pacific SST Departures ( o C) Time Longitude http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf During May-September 2013, well below-average SSTs were observed over the eastern half of the Pacific. In the last couple of weeks, SSTs have been below average across the eastern equatorial Pacific. Recently, above average SSTs in the western Pacific have expanded eastward to 160ºW.
WHAT S GOING TO HAPPEN IN THE FUTURE???
Scripps El Nino Forecast Model Forecast for next winter Model is predic9ng an El Nino for next year
Pacific Niño 3.4 SST Outlook Most models predict ENSO-neutral (-0.5ºC to +0.5ºC) to continue through the Northern Hemisphere spring. After that, models predict either ENSO-neutral or El Niño (greater or equal to +0.5ºC) during the Northern Hemisphere summer 2014. Figure provided by the International Research Institute (IRI) for Climate and Society (updated 18 February 2014).
Last year s forecasts:
Last year s forecasts: X = What really happened in Sep-Oct-Nov 2013
JET STREAM CONSTANTLY MEANDERING ==> Does not maintain a fixed position DURING EL NINO EVENT: ==> More likely that jet streams will be intense and over California ==> However, there are times when jet streams will be weak and/or not over California
JET STREAM CONSTANTLY MEANDERING ==> Does not maintain a fixed position DURING EL NINO EVENT: ==> More likely that jet streams will be intense and over California ==> However, there are times when jet streams will be weak and/or not over California # OF DAYS WITH STRONG JET STREAM OVER CALIFORNIA Non El Nino Year El Nino Year 15 50 WRONG TO SAY EL NINO STORM BECAUSE WE DO GET THESE TYPES OF STORMS IN NON EL NINO YEARS, BUT USUALLY NOT AS MANY
JET STREAM CONSTANTLY MEANDERING ==> Does not maintain a fixed position DURING EL NINO EVENT: ==> More likely that jet streams will be intense and over California ==> However, there are times when jet streams will be weak and/or not over California Non El Nino Year El Nino Year # OF DAYS WITH STRONG JET STREAM OVER 15 50 CALIFORNIA INSTRUCTOR S OPINION!!! WRONG TO SAY EL NINO STORM BECAUSE WE DO GET THESE TYPES OF STORMS IN NON EL NINO YEARS, BUT USUALLY NOT AS MANY
ECONOMIC IMPACT: El Niño impacts important business variables like sales, revenues, and employment in a wide range of climate-sensitive industries and sectors. Overall, total U.S. economic impacts of the 1997-1998 El Niño were estimated to be on the order of $25 billion. - NOAA Magazine Report