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 Key observations by Klaus Wyrtki in 1970’s El Nino is preceded by a transfer of warm water from west to east This transfer is thought to trigger a warm event What 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

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. Kelvin Rossby

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.

Normal Conditions in the tropical Pacific Sea level pressure Sea surface temperatures Trade winds Walker circulation Equatorial upwelling Thermocline depth Sea surface height Tropical rainfall patterns

El Niño Conditions Sea level pressure Sea surface temperatures Trade winds Walker circulation Equatorial upwelling Thermocline depth Sea surface height Tropical rainfall patterns

La Niña Conditions Sea level pressure Sea surface temperatures Trade winds Walker circulation Equatorial upwelling Thermocline depth Sea surface height Tropical rainfall patterns

What’s going to happen? Forecasts courtesy of IRI (Lamont-Doherty)

SSTanomalies this week (5-11 Oct. 2014)

What will next week/month/quarter look like? ?

Hawaii Drought Indonesia Flooding Societal impact of ENSO in the news 2010 news…

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

The disease is highly seasonal and follows the rainy season with a lag of about 2 months Malaria and Rainfall

ENSO and Zimbabwe corn yield + - ENSO

Predictions and Policy Snapshots 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

ENSO Prediction Methods Skillful 6-9 months into the future This ability has saved many millions of lives Two methods: Dynamical vs. Statistical

El Niño Forecasting Stephen E. Zebiak Senior Research Scientist International Research Institute for Climate Prediction Mark Cane DEES Vetlesen Professor

Real Time Ocean Observations ARGO floats XBT (eXpandable BathiThermograp h) Moorings Satellite SST Sea Level M.A. Balmaseda ( ECMWF)

ARGO drift sensors

TOGA TAO mooring array M.A. Balmaseda ( ECMWF)

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 Tropopaus e

Climate Models

Winds, Heat fluxes 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=t 0 Atmosphere modelOcean model FORECAST Forecast Initialization Procedures

Modeling gives you skill at forecasting: Better skill after 3-4 months than “persistence” Skillful up to 9 months into future

Correlation Skill for NINO3 forecasts

NINO3 Predictions

ENSO Prediction “Plumes”

How to predict? Forecasts courtesy of IRI (Lamont-Doherty)

How is forecasting possible? The tropical ocean-atmosphere system is coupled. Models are initialized with real observations The system has persistence (“memory”)