[Source: NOAA Climate Prediction Center, http://www.cpc.ncep.noaa.gov/
The daily Antarctic Oscillation (AAO) index is constructed by projecting the daily (00Z) 700mb height anomalies poleward of 20S onto the loading pattern of the AAO.
The daily AAO index and its forecasts using MRF and Ensemble mean forecast data are available for the previous 120 days and they are normalized by standard deviation using 1979-2000 base period. A 3-day running mean is applied for the forecast indices.
The monthly mean AAO index is available from January 1979 to the present.