The description of Australian pressure fields by principal components

The statistical method of principal components, when applied to mean sea level pressure data from the Australian region, shows that, in addition to the well‐known eastward succession of cyclones and anticyclones and the zonal pressure index type of oscillation, an important source of pressure variability is a quasi‐periodic oscillation of pressure over the eastern Australian region, which has ‘periods’ considerably longer than those due to the normal succession of cyclones and anticyclones. These several effects are revealed in the first three principal components which together account for 75 per cent of the total pressure variation.