Monthly Southern Hemisphere Annular Mode (SAM) Index
or Antarctic Oscillation (AAO) Index
The monthly SAM index (SAMI) or AAO index (AAOI) is defined as the difference in the normalized monthly zonal-mean sea level pressure (SLP) between 40°S and 70°S (Nan and Li, 2003). This SAMI is a modification of the AAO index defined by Gong and Wang (1999), which is the difference in the normalized zonal-mean SLP between 40°S and 65°S. The modified SAMI is used here because the negative correlation in the zonal-mean SLP anomalies between 40°S and 70°S is stronger than that between 40°S and 65°S. The daily SAM index (SAMI) or AAO index (AAOI) is defined as same as monthly index except for the daily resolution.
Correlation maps between monthly SLP anomalies in the SH (1979.1-2000.12) and (a) the SAMI (Nan and Li, 2003) and (b) the AAO index (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/monthly.aao.index.b79.current.ascii). The contour interval is 0.1. The red (blue) shading indicates significant at the 99.9% confidence level.
The Southern Hemisphere Annular Mode (SAM) Index
The SAM index. Top. DJF (1948-2010); Middle. JJA (1948-2010); Bottom. Annual (1948-2010)
The yellow lines indicate 7-year Gaussian-type filtered values.
- Feng, J., J. P. Li, and Y. Li, 2010: Is there a relationship between the SAM and southwest Western Australian winter rainfall?. J. Climate, 23, 6082-6089. PDF
- Wu, Z. W., J. P. Li, B. Wang, and X. H. Liu, 2009: Can the Southern Hemisphere annular mode affect China winter monsoon? J. Geophys. Res., 114, D11107, doi:10.1029/2008JD011501. PDF
- Nan, S. L., and J. P. Li, 2003: The relationship between summer precipitation in the Yangtze River valley and the previous Southern Hemisphere Annular Mode. Geophys. Res. Lett., 30(24), 2266, doi: 10.1029/2003GL018381. PDF
- Li, J. P., 2005: Coupled air-sea oscillations and climate variations in China, in: Climate and Environmental Evolution in China (First Volume), Edt. D. Qin, Beijing: China Meteorological Press, 324-333. PDF
- Gong, D. Y., and S. W. Wang, 1999: Definition of Antarctic Oscillation Index, Geophys. Res. Lett., 26: 459-462. PDF
- Thompson, D. W. J., and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13, 1000-1016. PDF
SAM index (AAO index)
You can download this file from here (right-click then select "Save Target As" or "Save Link As").
for year = 1948 to 2012
format (i7, 18f7.2) year, 12 * monthly value, DJF, MAM, JJA, SON, annual, and DJFM values
Note: (1) Missing values represented by -99.99;
(2) The reference period is 1958-2000;
(3) DJFM / DJF SAM indices: The DJFM index value for year N refers to an average of December year N and January, February, and March year N+1 indices values (Example: The 1948 index value was based on the average of December 1948 and January, February, and March 1949 indices values).