enso prediction and policy
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ENSO Prediction and Policy. Why Predict ENSO? How do we predict ENSO? Why is it possible ? What information do predictions offer? What to do with this information? An on-the-ground policy application…. Why does ENSO State tend to Oscillate?. Equatorial ocean dynamics - PowerPoint PPT PresentationTRANSCRIPT
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ENSO Prediction and Policy
• Why Predict ENSO?
• How do we predict ENSO?
• Why is it possible ?
• What information do predictions offer?
• What to do with this information?
• An on-the-ground policy application…
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Why does ENSO State tend to Oscillate?
Equatorial ocean dynamicsKey observations by Klaus Wyrtki in 1970’sEl Nino is preceded by a transfer of warm water
from west to eastThis transfer is thought to trigger a warm eventWhat triggers the movement of water?
– In cold phase, waters cold (and low) in east, warm (and high) in west
– Warm water from west sloshes back and overshoots equilibrium- positive feedbacks mentioned before set of El Niño conditions
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Why does ENSO State tend to Oscillate?
Shortest Answer: Equatorial ocean dynamics
Short answer: Differing timescales of Kelvin and Rossby Wave propagation
Longer answer: The oscillation is made possible due to the asymmetry between eastward and westward oceanic motions (see 2-D Animation in notes).
Along the equator there is a relatively fast eastward motion called an equatorial Kelvin wave. Peaking somewhat off the equator are westward motions called Rossby waves. Time scale: <1 yr for the Kelvin waves to shift the warm pool eastward [once trades relax]; 2 yrs for the Rossby waves to return the warm pool to the west, to await another wind relax.
KelvinRossby
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Here is a 3-D animation the tropical Pacific as it cycles through an El Niño then La Niña event. The surface shown is sea-level (in cm) and the surface is colored according to the SST anomalies associated with each event.
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Normal Conditions in the tropical Pacific
Sea level pressureSea surface temperaturesTrade winds Walker circulationEquatorial upwellingThermocline depthSea surface heightTropical rainfall patterns
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El Niño Conditions
Sea level pressureSea surface temperaturesTrade winds Walker circulationEquatorial upwellingThermocline depthSea surface heightTropical rainfall patterns
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La Niña Conditions
Sea level pressureSea surface temperaturesTrade winds Walker circulationEquatorial upwellingThermocline depthSea surface heightTropical rainfall patterns
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What’s going to happen?
Forecasts courtesy of IRI (Lamont-Doherty)
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SSTanomalies this week (5-11 Oct. 2014)
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What will next week/month/quarter look like?
?
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Hawaii DroughtIndonesia Flooding
Societal impact of ENSO in the news
2010 news…
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How ENSO impacts people
Effective management of climate related risks (opportunities) for improved:
• Agricultural production– Stocking, cropping calendar, crop selection, irrigation, insurance,
livestock/trade
• Water resource management– Dynamic reservoir operation, power generation, pricing/insurance
• Food security– Local, provincial, regional scales
• Public health– Warning, vaccine supply/distribution, surveillance measures,…
• Natural resource management– Forests/fire, fisheries, water/air quality
• Infrastructure development
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Month
JULMAYMARJANNOVSEP
200
100
0
Rainfall (mm)
Malaria incidence
The disease is highly seasonal and follows the rainy season with a lag of about 2 months
Malaria and Rainfall
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ENSO and Zimbabwe corn yield
+
-
ENSO
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Predictions and PolicySnapshots of current conditions
are not very useful.
People need advance warning, and for their region.
Today:
1) how predictions are made
2) what we can do with them
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ENSO Prediction Methods
• Skillful 6-9 months into the future• This ability has saved many millions of lives• Two methods: Dynamical vs. Statistical
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El Niño Forecasting
Stephen E. ZebiakSenior Research Scientist
International Research Institute for Climate Prediction
Mark CaneDEES
Vetlesen Professor
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Real Time Ocean ObservationsARGO floats
XBT (eXpandable BathiThermograph)
Moorings
Satellite
SST
Sea Level
M.A. Balmaseda ( ECMWF)
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ARGO drift sensors
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TOGA TAO mooring array
M.A. Balmaseda ( ECMWF)
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Surface layer
Deep ocean; u=v=w=0
Active layer
50 m
150 m
Simplified Ocean and Atmosphere Models
Simplified form of equations for conservation of mass, momentum, energy
SSTA
Tropopause
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Climate Models
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Winds,Heatfluxes
Ocean simulation
Ocean obs.
Ocean analysis
t t + t
SST forcing
Atmos. simulation
Atmos. obs.
Atmos. analysis
t t + t
Data assimilation
Initial Conditions, t=t0
Atmosphere model Ocean model
FORECAST
Forecast Initialization Procedures
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Modeling gives you skill at forecasting: Better skill after 3-4 months than “persistence”Skillful up to 9 months into future
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Correlation Skill for NINO3 forecasts
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NINO3 Predictions
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ENSO Prediction “Plumes”
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How to predict?
Forecasts courtesy of IRI (Lamont-Doherty)
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How is forecasting possible?
The tropical ocean-atmosphere system is coupled.
Models are initialized with real observations
The system has persistence (“memory”)