El Niño/Southern Oscillation (ENSO)

El Niño Status

Latest SST and OLR Maps

Plot of SST monthly anomalies
Latest Monthly SST

Time-Lat Pacific SST plot
Plot of OLR seasonal anomalies
Latest Seasonal OLR

SST and OLR Animations

Plot of SST monthly anomalies
SST loop over last year
Plot of OLRmonthly anomalies
OLR loop over last year

Projection on the ENSO optimal structure

PSD Maproom

  • PSD's maproom contains a complete set of atmosphere ocean monitoring products.

ENSO indices

Single Indices attempt to represent ENSO processes with a single number.
While this can oversimplify the physics, single values can be useful as a short hand
and as an easy way to examine historic ENSO

Combined Variable El Niño index (MEI)

MEI time series

Southern Oscillation Index:

Sea Surface Temperature Timeseries:

Other Indicies:`
Oceanic Nina Index (ONI)

Trans Nina Index (TNI)

Science Background

  • What happens during an "El Niño/La Niña" cycle? Example: A 3-D animation of the tropical Pacific ocean during a simulated ENSO cycle.
  • Annual Cycle: what is normal for the atmosphere and ocean?

PSD Research Topics

PSD Posters

PSD Publications

Publications from Other Sites

Other Research Institutions that research ENSO

El Niño and La Niña can cause the "seasonal climate" -- the cumulative effects of the weather over a season -- to deviate from normal at many places around the globe. These pages analyze what happened during past El Niños and La Niñas and provide a guide to what may happen in the future.

What is the average (composite) climate associated with ENSO

 o Seasonal El Niño and La Niña climate means and anomalies
Allows single or comparison plots of seasonal averaged variables in relation to El Niño and La Niña over the globe and the US.
 o Monthly El Niño and La Niña composites
What does the seasonal cycle of different variables during an average (composite) El Niño and La Niña look like?
 o Animations of global seasonal temperature and precipitation composites
Plot animations and also composite signals based on historical data of global surface temperature and precipitation.
 o Composite wintertime US temperature and precipitation means and anomalies
Posters show the El Niño/La Niña temperature and precipitation anomalies on one page. Postscript versions are available (2.8M) for the means and anomalies.

Risk Analysis

Risk analysis shows the relative odds of seasonal extremes during an event rather than the average response to an event. On some regions, one may see the same sign response in all events while in another, one might just see 2/3 of the years having the same sign response.

 o Plot effects on seasonal climate extremes of temperature and precipitation over the United States ("Risk Plots")
Given an El Niño or La Niña condition, what are the odds of getting a warm versus a cold season? A wet versus a dry season?
 o Regional seasonal temperature and precipitation extremes with preceding and concurrent ENSO conditions.
Historical risk of seasonal temperature and precipitation extremes for specific regions of the United States. Risk is shown with the ENSO conditions preceding the seasonal value from 3 seasons to 0 seasons.
 o Posters
These "posters" show the comparison of actual climate throughout the year during a El Niño and La Niña event to those expected from a risk analysis of the historical climate record for the last 100 years. Surface temperature and precipitation are plotted. Note that these posters are large.

How events differ

 o Plots showing differences between the atmospheric response of El Niño and La Niña events.
Both differences in the tropical SST pattern and "random" variability of the the atmosphere mean that the climate of El Niño and La Niña events will not necessarily be the same from event to event.
The ability to forecast El Nino and La Nina events is extremely important as these events tend to be associated with consistent climate anomalies in the tropics and can even influence the atmosphere in midlatitudes. Forecasts are of two types; those obtained from various coupled ocean/atmosphere models those obtained from statistical models (from simple to complex). These models vary in their skill and sometimes can even do better during certain phases of ENSO than others. Forecasters try to take all this in account when making predictions.

PSD Experimental ENSO Forecasts

Linear Inverse Modeling SST/ENSO Forecast
Linear Inverse Modeling Seasonal Plot

Experimental statistical forecasts of SST anomalies based on current initial conditions. SST data used in these forecasts have been provided by NCEP, courtesy of R. W. Reynolds. Contour interval is 0.3 degrees C.

Experimental Tropical C-LIM "Coupled" LIM forecast plot lag4

CLIM is user to create forecasts of Tropical Convection, Wind, and SST for out to 200 days.

Types of ENSO Forecasts

Different Models are used to predict ENSO and the associated SST anomalies.

  1. Global Dynamic Models: These are computer models that contain explicit includion of atmospheric processes. A forecast is calculated for each time step. Models have different spatial and temporal resolutions. Some models have a nested higher resolution regional model that is surrounded a lower resolution global model. Some models have fully coupled atmopshere and oceans while some are just atmospheric with SST prescribed. Many models are run in "ensemble mode" in which small perturations are applied to an initial condition in order to better represent chatic processes of the atmospheric. There are tradeoffs in what and how physical processes are included, in the spatial and temporal scales and in the number of ensmebles used. Some of the models used in ENSO forecasting are NCEP's CFS, the GFDL...
  2. Statistical: Statistical models use historic data to create predictions. These can range from very simple models such as linear regression forecast of SST at a point using past SST to a much more sophisticated model such as LIM where there dynamical relationsip between past and future data that can be used and tested. Other examples of statisticl models includ CCA, .

Other ENSO forecast Resources

PSD's El Niño FAQ

 * How will El Niņo impact a particular region of the world?
 * What are the predictions for El Niņo?
 * What is the SOI (Southern Oscillation Index)?
 * When is the MEI updated? How can I get those numbers?
 * Can I use PSD plots and how do I acknowledge PSD?
 * What is the most recent SST/El Niņo data available?
 * What is a good source of El Niņo information for young people?
 * What is source of El Niņo/La Niņa information for adults?
 * How do I get climate data to look at El Niņo myself.
 * What years are El Niņo/La Niņa years.
 * What is the difference between El Niņo, ENSO and the Southern Oscillation?
 * Who are good contacts for reporters?
 * Where can I find other ENSO FAQs?

How will El Niņo impact a particular region?

There has been a lot research investigating the effects of El Nino/Southern Oscillation on climate (temperature, rainfall, snowpack, climate extremes etc.) throughout the world. The research has been compiled at several web sites including Note that there are very few regions where the effects of El Niņo/La Nina are consistent every year due to both the varying nature of El Niņo and the inherent variance of the atmosphere/ocean system. The research is best utilized to indicate the probability of what the effects will be.

What are the predictions for El Niņo?

Official predictions for El Niņo are produced by the Climate Prediction Center. Unofficial forecasts based on different models and/or statistical techniques are also available at several locations.

When is the MEI updated? How can I get those numbers?

The MEI is generally updated by the 3rd workday of the month. If you are interested in obtaining the numbers used in the plot or want further information about how the index is derived, please contact Klaus Wolter klaus.wolter@noaa.gov

Can I use PSD plots and how do I acknowledge PSD?

You can use any PSD generated plot (either from a pregenerated figure or from an interactive program). We ask that you acknowledge the PSD in the publication. For example, "Image provided by the NOAA/OAR/ESRL PSD, Boulder Colorado from their Web site at http://www.esrl.noaa.gov/psd/".

What is the most recent SST/El Niņo data?

NOAA's PMEL maintains a list of the most recent data/plots available.

What is a good source of El Niņo information for young people?

See PSD's ENSO educational resource page.

What is source of information for adults?

There are numerous webpages that have information about El Niņo. Some of the more "complete" websites that have links to data, research, predictions and so forth are the NOAA El Niño page, the NOAA PMEL web page and the NOAA/CPC ENSO pages.

How do I get climate data to look at El Niņo myself?

PMEL maintains a list of El Niņo related data sources. Other sources of data include the National Climate Data Center (NCDC) (basic station data on daily and monthly time scales), the National Snow and Ice Data Center (NSIDC), the National Geophysical Data Center, National Oceanographic Data Center (NODC), National Center for Atmospheric Research (NCAR) Data Archive and the meteorological FAQ.

What years are El Niņo/La Niņa years?

Definitions for what constitute an El Niņo/La Niņa event as well as events themselves vary so there is not a definitive set of years. However, PSD (from Smith and Sardeshmukh and Kiladas and Diaz), CPC (ONI from the NOAA ERSST3) , COAPS and FSU maintain a list of years used in their research. In addition, PSD makes available the MEI and the extended MEI index and CPC has a list of various atmospheric/ocean indexes from 1950 that can be used to determine ENSO years. NASA has a precipitation based ENSO timeseries called the ESPI. Some ENSO timeseries are available from 1871 at PSD's GCOS Timeseries webpage. More indices are available at PSD including the MEI.

What is the SOI (Southern Oscillation Index)?

The cyclic warming and cooling of the eastern and central Pacific can be seen in the sea level pressure in the region. In particular, when the pressure measured at Darwin is compared with that measured at Tahiti, the differences between the two can be used to generate an "index" number. A positive number indicates La Niņa (eastern tropical Pacific ocean cooling) and a negative number indicates El Niņo (or ocean warming). Historical and recent values can be found at the Climate Prediction Center. PSD has a historical perspective on the SOI.

What is the difference between El Niņo, ENSO and the Southern Oscillation?

El Niņo refers to the oceanic component of the El Niņo/Southern Oscillation system, the Southern Oscillation to the atmospheric component and ENSO to the coupled system. In practice, El Niņo is sometimes used to refer to the entire system.

Who are good contacts for reporters?

The Office of Oceanic and Atmospheric Research has a list of media contacts.

NOAA also has a department of department of external affairs

Where can I find other ENSO FAQs?

Other Links

El Niņo/Southern Oscillation Education Resources

Please email me if you know of other ENSO web educational resources.

Datasets Useful for ENSO Research


Gridded SST datasets are available for monthly means and for daily. Values can be mean or anomalies. Gaps usually exist in SST dataaets both in space and time. Different datasets use different models to fill in gaps.
DatasetsAreal CoverageGrid SizeTime StepTime CoverageLevels
CRU Air Temperature and Combined Air Temperature/Marine Anomalies V3 Global5.0°x5.0° Monthly1850-presentNone
ICOADS Global2.0°x2.0°,1.0°x1.0° Monthly1800-presentNone
Kaplan SST Global5.0°x5.0° Monthly1856-presentNone
NCEP GODAS ocean analysis Global.3°x.3° Monthly1980-present 40
NCEP/NCAR Reanalysis Global2.5°x2.5°, T42 Gaussian, T62 spectral 4X Daily, Daily, Monthly1948-present17 pressure levels, 28 spectral
NOAA Extended Reconstructed SST V3b Global1.0°x1.0° Monthly1854-presentNone
NOAA High-resolution Blended Analysis of Daily SST and Ice. Global.25°x.25° Daily1981-present None
NOAA Merged Land-Ocean Surface Temperature Analysis (MLOST) V3.5.4 Global1.0°x1.0°2.5°x2.5° Daily1940-2011None
NOAA Optimum Interpolation (OI) SST V2 Global1.0°x1.0° Monthly,Weekly1981-presentNone
NODC (Levitus) World Ocean Atlas 1994 Global1.0°x1.0° Monthly,AnnualClimoNone
NODC (Levitus) World Ocean Atlas 1998 Global1.0°x1.0° Monthly,AnnualClimoNone


Outgoing Long Wave Radiation (OLR) is a measure of tropical convection and has been available via satellite observations since the early 1970's. We make available gridded interpolated values as well as the provided directly from NCEP (which are more recent).
DatasetsAreal CoverageGrid SizeTime StepTime CoverageLevels
Interpolated OLR Global2.5°x2.5° Daily,Monthly1979-near presentNone
Uninterpolated OLR Global2.5°x2.5° Daily1991-presentNone

Time Series

While ENSO is a process that varies both in space and time, it can be convenient to use single time series to represent in monitoring and analysis. Some of these time series are SST averages in a specific region of the tropical Pacific while others use more than 1 variable to attempt to capture more of the dynamical processes that occur in ENSO.
NameRegionDate Range
Multivariate ENSO index: MEITropical Pacific1950-present
Extended Multivariate ENSO index: MEI.extTropical Pacific1871-2005
Nina 1.21871-present
Nina 3 SST 5N-5S,150W-90W1871-present
Nina 3.4 SST 5N-5S,150W-90W1871-present
Nina 4SST 5N-5S,150W-90W1871-present
TNIDifference Nina 1.2 and Nina 41871-present
SOIDifference SP Tahita and Darwin1871-present

Other datasets

As ENSO impacts weather and climate in general, researchers need to potentially look at all atmosperic and ocean variables. PSD maintains an extensive collection of gridded datasets. Other dataset can be found from links on PSD's data information webpage. Some other NOAA sites also link to ENSO related datasets: for example,PMEL has an ENSO data source list.