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Michelle L’HeureuxENSO Team Lead
NOAA Climate Prediction Center (CPC)
March 2012
El Niño – Southern Oscillation (ENSO) Monitoring and Prediction at
NOAA Climate Prediction Center (CPC)
El Niño – Southern Oscillation (ENSO) Monitoring and Prediction at
NOAA Climate Prediction Center (CPC)
• Monitoring and prediction products at NOAA CPC
• Procedures on how we create and disseminate a forecast
• Current skill of ENSO prediction models
• How ENSO information is used in seasonal prediction
Outline
We deliver climate prediction, monitoring, and diagnostic products for timescales from weeks to years to the Nation
and the global community for the protection of life and property and enhancement of the economy.
Mission of NOAA Climate Prediction Center
• The El Niño-Southern Oscillation (ENSO)
• Longer-term trends (use past 10-15 year average of temperature and precipitation)
• In general, boundary conditions like global sea surface temperatures (SST) and land surface variables (soil moisture, sea ice, snow cover) are used
What are the primary sources of skill in seasonal climate outlooks for the U.S.?
What datasets do we rely on to monitor and predict ENSO?
In situ observations: ships, TAO moored buoys, and drifting buoys like Argo
Geostationary satellites like GOES and polar orbiting satellites like POES and Suomi
Various gridded reconstructions of Sea Surface Temperature (SST) (e.g. ERSST, OISST)
Gridded Reanalysis products, which combine observations with a first-guess model forecast to fill gaps (e.g. NCEP/NCAR, CFSR)
SST and reanalysis are run in “real-time.” For historical comparisons, homogeneity of the dataset is desired.
What products do we use to monitor ENSO?
Weekly and monthly graphics of the tropical Pacific:* sea surface temperature (SST)* subsurface temperature* sea level pressure (i.e. SOI) * outgoing longwave radiation (OLR) * Various levels of winds (850/200-hPa)* velocity potential + streamfunction
What products do we use to predict ENSO?
(1) Dynamical models: large number of observations, mathematical equations that describe large-scale physical relationships, and parametrizations of smaller sub-grid features (run on supercomputers)
- NCEP Climate Forecast System (CFS): a tier-one coupled model (ocean and atmosphere interact freely)
(2) Statistical models: uses a smaller number of observed variables (~1-3) and past statistical relationships (run on a personal computer)
- CPC Constructed Analog (CA), Canonical Correlation Analysis (CCA), and Markov (MKV)
(3) Multi-model combinations: uses several dynamical and/or statistical models and combining them through various statistical methods
- CPC Consolidated Forecast Tool (“CON”): combines models using an ensemble regression based kernel distribution (see Unger et al., 2009)
- IRI/CPC ENSO Prediction “Plume” which shows ~20+ dynamical and statistical models and shows the dynamical and statistical model averages
What products do we use to predict ENSO?
Where are these products located?
ENSO products are on CPC's website (weekly + monthly updates):http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtmlhttp://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtmlhttp://www.cpc.ncep.noaa.gov/data/indices/
NCEP Climate Forecast System ENSO prediction (daily update):http://www.cpc.ncep.noaa.gov/products/CFSv2/CFSv2seasonal.shtml
CPC “Consolidation (CON)” ENSO prediction (monthly update):http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/unger.pri.php
Ocean Monitoring products (+ monthly briefing): http://www.cpc.ncep.noaa.gov/products/GODAS/
Global Tropics Benefits/Hazards product for Week-1 and Week-2 (weekly briefing):http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/index.phphttp://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
NOAA's Official ENSO Index:Oceanic Niño Index or “ONI”
The ONI is a 3-month running average of SST anomalies in the Niño-3.4 region of the east-
central equatorial Pacific Ocean.
Retrospectively, we use 5 consecutive 3-month ONI > 0.5°C as an El Niño episode and ONI < -0.5°C as La Niña episode.
Dataset: ERSSTv3b, which is a 2°x2° gridded SST reconstruction (Smith et al., 2008) using in situ data and statistical relationships to fill in gaps and create a continuous, homogeneous SST record.
We only compute the ONI back to 1950 because data coverage is sparse prior to then.
An El Niño or La Niña Watch: Issued when the environment in the equatorial Pacific basin is favorable for the development of El Niño or La Niña conditions within the next six (6) months.
An El Niño or La Niña Advisory: Issued when El Niño or La Niña conditions in the equatorial Pacific basin are observed and expected to continue.
Final El Niño or La Niña Advisory: Issued after El Niño or La Niña conditions have ended.
NA: The ENSO Alert System will not be active when El Niño or La Niña conditions are not observed or expected to develop in the equatorial Pacific basin.
The ENSO Alert System
The ENSO Alert System provides the public with a succinct summary of the status of ENSO.
El Niño conditions: one-month positive SST anomaly of +0.5 or greater in the Niño-3.4 region and an expectation that the 3-month ONI threshold will be met.
La Niña conditions: one-month negative SST anomaly of −0.5 or less in the Niño-3.4 region and an expectation that the 3-month ONI threshold will be met.
AND An atmospheric response typically associated with El Niño/ La Niña over the equatorial Pacific Ocean.
The ENSO Alert System is based on El Niño and La Niña “conditions” that allows the NOAA to be able to issue watches/ advisories in real-time.
The value of the ONI is to define episodes retrospectively.
What is the criteria for an ENSO Advisory?
Can click on status to get detailed information on Alert System
definitions
http://www.cpc.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html
ENSO Alert System is updated with the “ENSO Diagnostic Discussion”
NOAA's monthly ENSO Diagnostic Discussion is used to update the ENSO Alert System status.
Also gives a short ~3 paragraph summary of the current observations and prediction of ENSO.
How is the monthly ENSO Diagnostic Discussion put together?
Step #1: Send out forecaster spreadsheets to the ENSO team (9 people). They are given ~2.5 days to consider analysis and then give their individual forecast.
Step #2: All team member forecasts are combined. We show the probability of each ENSO category out to ~8 leads.
Step #3: Lead author writes the initial draft and it is iterated on by the internal ENSO team. Eventually the draft is sent for comments by external NOAA employees outside of CPC. – If a change in status, NOAA leadership and public affairs are notified.
Step #4: The discussion is finalized and translated into Spanish by weather forecast office in San Juan.
Each forecaster has expertise in different areas and tends to weight different aspects of ENSO. In general, the forecasters rely on:
(1) Various ENSO-related monitoring products
(2) Dynamical and statistical models and multi-model combinations
(3) Their knowledge and experience of previous ENSO episodes
What do the ENSO forecasters examine?
How is the forecasters input synthesized?
Each forecaster fills out a spreadsheet with probabilities of three categories (El Niño – Neutral – La Niña). All forecasts are averaged to create the probabilities. See example below:
• Discussion is posted to CPC website. There is also an email listserv which has 10,000+ subscribers (includes technical experts, media, general public, etc.).
• Within hours, NOAA posts a press release (if a noteworthy change in ENSO) and articles will appear on media outlets (Reuters, Bloomberg, AP, etc.)
• NOAA/NWS has several public affairs officials who are available to arrange interviews radio, TV, newspapers, blogs….
How is the monthly ENSO Diagnostics Discussion distributed to the Public?
• Recently, dynamical models have slightly edged statistical models in forecast skill (Barnston et al. BAMS, in press)
• Models have trouble with transition timing and predicting amplitude of ENSO events.
• Stronger ENSO events tend to be better predicted than weaker ones.
• From decade-to-decade, ENSO prediction skill can vary widely due to natural internal variability (can overwhelm forecast model improvements).
• “Spring prediction barrier:” historically, forecasts before the Northern Hemisphere Spring have low skill.
• Intraseasonal variability (i.e. MJO) is not captured in most of these models and these phenomenon can have considerable impact on ENSO evolution.
How well do models predict ENSO?
From Barnston et al. (BAMS, in press) “Skill of Real-Time Seasonal ENSO Model Predictions during 2002-2011– Is our Capability Increasing?”
Orange/Red Shading: Higher correlations (more skill)
White/Blue: Lower correlations ( 0 < r < 0.5)
Light Grey: Negative correlations (very poor skill!)
Lead Time (0-8 months) is on Y-axis and Target Season is on the X-axis
The orange box designates the statistical models (the rest are dynamical)
Anomaly Correlations of ENSO models from 2002-2011
Anomaly Correlations and Root Mean Squared Error (RMSE) of ENSO models (all months from 2002-2011)
Correlation by Lead Time RMSE (standardized units) by Lead Time
Lead (months) Lead (months)80 80
0
1
0
1.2
• At 0-month lead, ENSO model skill ranges from 0.75 to 0.95.
• At 6-month lead, ENSO model
skill ranges from 0.1 to 0.7.
• For lead times greater than 2 months, RMSE of “persistence” is greater than all models.
• In general, models with high correlation tend to have low RMSE.
Lead (months)
Anomaly Correlations by Lead Time
Top Panel: May-Sept
Target
Bottom Panel: Nov-Mar
Target
0 8
0
1
0
1
At 6-month lead:
ENSO model skill ranges from below zero to 0.55 during
boreal summer
ENSO model skill ranges from 0.45 to 0.9 during boreal
winter
0 8
Top Panel: 3-year sliding Correlation based on Hindcasts (1981-2010) Bottom Panel: 3-year sliding standard deviation of Niño-3.4
ENSO model skill decreased during
2002-10 (and in early-mid 1990s) in part due to the observed ENSO
variability (lower amplitude ENSO events and more transitions between phases)
Input from ENSO updates are incorporated into other CPC products and services: Seasonal and Monthly Outlooks, Drought Outlook, Fire Potential conference call, U.S. and Global Hazards, etc.
Who benefits from these climate outlooks?
A few examples:
1. NOAA climate outlooks provide big picture context for the weather events. This gives local TV weather forecasters and the private sector increased opportunity to add value to their forecasts, and to tell a better story.
2. Electric power companies have used climate forecasts for decades to make decisions relevant to energy trading.
3. U.S. federal government agencies, including FEMA, Department of Interior, Department of State, Military use them for planning purposes and resource allocation.
4. Local and State governments use them to allocate resources, e.g., California has used prediction of El Nino to maintain drainage canals.
How is ENSO used in seasonal temperature and precipitation outlooks?
First, some quick background on our seasonal outlooks:
Seasonal outlooks are probabilistic (given in % chance) reflecting the fact that confidence is lower than a deterministic weather forecast.
Precipitation and Temperature (P&T) outlooks are given for three (“tercile”) categories: above average/median – near average/median – below average/median
Probabilities either reflect a “tilt in the odds” or “favoring” of a certain category or “Equal Chances (EC)” which means no category is favored (33.3% – 33.3% – 33.3%).
“Reliable”: Over a long enough time period, the forecast probability reflects how often that category actually occurred. – given a forecast for a 60% chance of above-average temperatures, one would expect above average temperatures to occur 60% of the time.
“Sharpness:” a high probability issued for the correct observed category
“Discrimination:” If outcomes are different, are the forecasts different? The probability of a forecasted category should increase when that observed category occurs (probability should decrease when the category occurs less)– If forecast is always the same regardless of actual observation, then no discrimination
“Resolution:” If forecasts are different, are the outcomes different? The probability of a forecasted category should be different when the observed outcome is different. – If the outcome is always the same regardless of the forecasts, then there is no resolution. – Even if the forecast is always wrong, it has high resolution if it can distinguish between outcomes.
Great verification reference: http://www.cawcr.gov.au/projects/verification/
Some desired quantities of a seasonal outlook (or a probabilistic climate forecast, in general)
How is ENSO used in seasonal temperature and precipitation outlooks?
ENSO impacts are already captured in dynamical climate model forecasts, like the NCEP Climate Forecast System (CFS) and the new National Multi-Model Ensemble (NMME).
However, several statistical tools (that are not conditioned on ENSO phase) do not resolve ENSO impacts over the U.S.
Some tools like Optimal Climate Normal (OCN), which captures the longer-term trends, do not incorporate ENSO impacts at all.
Thus, the seasonal forecaster will often weight the dynamical models more (over the statistical models) in the outlook during ENSO periods.
During ENSO periods, the forecaster often uses historical ENSO composites and boxplots in association with the model guidance.
ENSO Composites and Boxplots for the U.S.
Central Florida Precipitation (DJF)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#composite
Global ENSO Regression and Correlation Mapshttp://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#composite
• Gridded temperature anomalies (CPC GHCN) and precipitation anomalies (CPC Unified Precipitation) associated with the standardized Niño-3.4 index from 1948-2010.
• Assuming linearity so regression anomalies showing sign of El Niño (reverse for La Niña)
The IRI provides global seasonal climate outlooks outside of the United States
Recently, the IRI has become a close partner on NOAA's ENSO prediction team, assisting in the creation and dissemination of the ENSO outlooks. http://iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html
http://portal.iri. columbia.edu/
Summary
• NOAA CPC provides routine monitoring and prediction products for ENSO, which are available on our website.
• Once a month, the ENSO team determines the probabilities for each ENSO category, which provides the ENSO prediction for the upcoming ~8 seasons.
• A variety of ENSO models (statistical and dynamical) are considered to create the forecast. Over the past 10 years, dynamical models are slightly more skillful than statistical models.
• The ENSO outlook is incorporated (implicitly and explicitly) into CPC’ s monthly/seasonal temperature and precipitation outlooks and other products.
Miscellaneous Slides
Since 1995, what has been the performance of U.S. Seasonal Temperature and Precipitation
Outlooks?
Hedike Skill Score (HSS) is the percent improvement over random chance. No skill forecast = 0
Perfect forecast = 100Worse than random chance < 0
Temperature HSS Precipitation HSS
Mean = 22.3, Coverage = 50.9% Mean = 10.9, Coverage = 31.4%
• On a shorter, “subseasonal” timescale (i.e. weekly forecasts out to ~1 month): the Madden Julian Oscillation (MJO)
Other climate phenomenon impacting Peru?
Nov-Mar Precipitation Anomalies May- Sept Precipitation Anomalies
Timeline for Weekly ENSO Update
Updated each Monday (Tuesday if holiday):
6:30am: Many graphics are produced using NCEP data via an automated “cron” job
7 – 8:30am: Put together ENSO powerpoint (edit text, reformat some figures)
8:30 – 10am: Reviewed by ~3 other CPC employees
10 – 11am: Incorporate feedback
By 11am EST: Finalize and upload to the CPC web (Powerpoint and PDF)
Timeline for Monthly ENSO Diagnostics Discussion
Released on the Thursday between the 4th-10th of the month at 9am EST/EDT.
Mon. Tues. Wed. Thurs. Fri.
Email forecaster spreadsheets
Forecaster spreadsheets due
Initial Draft is completed
Draft is reviewed by ENSO team
Draft is emailed to Outside Collaborators
Spanish translation begins
Feedback from Outside Collaborators
Discussion is finalized. Spanish translation is finalized by WFO San Juan
ENSO Discussion is released
Email listserv
(Press Release if applicable)
Week before the Release
Week of the Release
