Antarctic Oscillation Index

 

 

Antarctic Oscillation refers to a large scale alternation of atmospheric mass between the mid-latitudes and high latitudes surface pressure. In order to understand the spatial structure of sea level pressure variation in detail, empirical orthogonal function analysis is applied. Above figure shows the EOF-1 for monthly mean SLP in southern hemisphere.(

An objective index of the Antarctic Oscillation Index (AOI) is defined as the difference of zonal mean sea level pressure between 40° S and 65° S, see the below figure. The AOI has the potential for clarifying climate regimes in the southern hemisphere, similar to how the NAO (North Atlantic Oscillation ) and the NPO(North Pacific Oscillation) has been used in the northern hemisphere.

 

aoi.jpg (12812 bytes)

Above is the AOI time series.

 

You can download the monthly Antarctic Oscillation Index data for the period 1949-2005 by click here (in pure text), normalized with respect to 1971-2000. Derived from NCEP/NCAR reanalysis SLP.

In addition, the Antarctic Oscillation index for 1850-2004 is also available here, which is computed from HadSLP2.

 

Related References

Gong D Y, and S W  Wang. Definition of Antarctic Oscillation Index, Geophysical Research Letters,1999,26:459-462 (Preprint in PDF Format)