20CR Climate Indices:AAO

Description:
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.
Image:
Spatial pattern of the AAO. EOF is based on 1981-2011 monthly anomalies of SLP from the 20CR V2 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).
Time Interval: Monthly
Time Coverage: 1871 to 2011
Update Status: none

Get Data:
AAO index: Standard PSD Format (What is standard format?)
AAO index: Standard PSD Format (1948 onwards version)(What is standard format?)
Source:
Data is calculated at PSD using method in paper below.
References:
  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