An assessment of relationships between the Australian subtropical ridge, rainfall variability, and high-latitude circulation patterns

The monthly anomaly of the latitude of the subtropical ridge over eastern Australia (L) is a major regulator of synoptic-scale influences on Australia's climate. Three datasets have been used to calculate L: observed Australia coastal mean sea level pressure (MSLP), Hadley and NCEP Reanalysis datasets. The choice of datasets used in this study appears to strongly influence results. Changes in the Southern Hemisphere Hadley cell and meridional circulation changes are associated with changes in L and it is shown that (1) L has statistically and physically significant relationships with seasonal rainfall in Australia; (2) the Antarctic Oscillation Index (AOI) has statistically significant relationships with Australian seasonal rainfall; and (3) L and Southern Annular Mode (SAM) are significantly related. Longer-term latitudinal shifts in L are also discussed. Copyright (C) 2008 Royal Meteorological Society