Current Year | Compare warm-SSTA years | Compare cool-SSTA years

Integrated Equatorial Pacific Zonal Wind Stress Anomaly

Zonal wind stress anomalies over the equatorial Pacific Ocean drive upper ocean circulation changes and equatorial Pacific sea surface temperature anomaly development associated with El Niño and La Niña events. During El Niño events, positive (eastward) equatorial zonal wind stress anomalies over the western and central part of the basin drive and maintian anomalous warming of sea surface temperatures to the east of the wind anomalies. During La Niña events, negative wind stress anomalies develop over the equatorial Pacific and drive anomalous surface cooling of central and eastern equatorial Pacific sea surface temperature. Chiodi (2019) found that arithmetic time integrals of zonal wind stress anomaly averaged along the oceanic waveguide (5S to 5N) and from 130E to 120W (the eastern edge of the Niño 3.4 region) were able to forecast end-of-year Niño 3.4 conditions (December ENSO year 0 through February ENSO Year +1) with skill comparable to more sophisticated air-sea coupled ENSO prediction models.

The 'Current Year' plot above shows this zonal wind stress integral as a running sum starting from March of the current ENSO period (ending February Year +1). Clicking on 'Compare warm-SSTA years' and 'Compare cool-SSTA years' will cycle through plots comparing the present year with several previous years.

Data source

The zonal stress anomaly integrals are calculated using winds from the tropical Pacific moored-buoy array and satellite-based scatterometers. The mooring-array winds are available from the Global Tropical Moored Buoy Array (GTMBA) office at NOAA's Pacific Marine Environmental Laboratory. The scattorometer data is used to fill gaps caused when direct observations from the traditional moored-buoy sites are unavailable. The scatterometer data is made available by Remote Sensing Systems and is based on surface backscatter measurements from the QuikSCAT instrument during 2000-2009 and the ASCAT-A instrument thereafter.

Calculation

The anomaly is calculated relative to a monthly climatological seasonal cycle based on the period 1 Jan 1992-present for the moored-buoy winds, and 2000-present for the scatterometer winds. In the mooring case, daily averaged winds are used to estimate wind stress. In the scatterometer case, 3-day averages are used. The monthly climatologies are linearly interpolated to determine daily anomalies.

Reference

Chiodi, A.M. (2019): Diagnosing and predicting ENSO SSTA development with TAO/TRITON and scatterometer winds. J. Climate, doi: 10.1175/JCLI-D-19-0183.1.

External Links

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Daily averaged winds from the tropical Pacific moored buoy array are available at the GTMBA site

Daily averaged winds are available from Remote Sensing Systems based surface roughness measurments from the QuikSCAT and ASCAT-A scatterometers.