20CR Climate Indices:AAO

This mode describes low frequency variability of the Southern Hemisphere extratropics. A positive index (lower polar pressure) is associated with stronger, zonal winds in the extratropics. A negative value is associated with weaker zonal winds.
Spatial pattern of the AAO. EOF is based on 1981-2010 monthly anomalies of SLP from the 20CRV3 dataset.
Calculation Method:
Our EOF is calculated using SLP from 20S to the pole from 1981 to 2010.Anomalies are calculated for each month based on a 1981-2010 climatology and all months are used in the calculation of the EOF. The grids are area-weighted via the cosine of latitude. The data is then projected back onto the EOF and standardized to produce the principal component (time-series) based on the 1981-2010 time period.
Time Interval: Monthly
Time Coverage: 1836 to 2015 (V3)
Update Status: None

Get Data:
AAO index 20CRV3: Standard PSL Format (What is standard format?)
AAO index 20CRV3: Standard PSL Format (1948 onwards version)(What is standard format?)
Data is calculated at PSL using method in paper below.
  1. Thompson D. W.J. and J.M. Wallace:2000: Annular Modes in the Extratropical Circulation. Part I: Month-to-Month Variability: J. of Climate, 13, 1000-1016.
  2. See annular modes webpage at Colorado State
Other Links
  1. JISAO Antarctic Oscillation (AAO) time series, 1948 - 2002
  2. NOAA/NCEP Climate Prediction Center (CPC) AAO monitoring page