Climate Variability: Oceanic Niño Index
First published: 2015
Brief summary
NOAA Climate Prediction Center ONI data used to classify ENSO events.
Article
The Oceanic Niño Index is a measure used by NOAA to monitor sea-surface temperature conditions in the central equatorial Pacific. It is based on temperature anomalies in the Niño 3.4 region, extending from 5°N to 5°S and from 120°W to 170°W.
The index uses a three-month running mean of sea-surface temperature anomalies. Anomalies are calculated relative to a set of centred 30-year climatological base periods that are updated periodically to account for long-term changes in the climate record.
El Niño conditions are associated with values at or above +0.5°C, while La Niña conditions are associated with values at or below −0.5°C. NOAA identifies historical episodes when these thresholds persist for at least five consecutive overlapping three-month seasons.
The ONI is a temperature-based indicator and does not by itself describe the full coupled ocean-atmosphere state. Operational assessments also consider winds, pressure, convection and forecast information when determining current ENSO conditions.
Source details and credits
- Source / publisher: NOAA CPC
- Source type: Data series
- URL type: WWW
- Credits: NOAA CPC
- URL: https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php