The Southern Oscillation. Part VII: meteorological anomalies over the Indian and Pacific sectors associated with the extremes of the oscillation

Abstract

In the year before the development of positive sea surface temperature anomalies in the central and eastern equatorial Pacific (Year -1 of a Warm Event), a strong South Pacific High is associated with below normal surface pressure over Australia and the Indian Ocean. This occurs concurrently with a poleward displacement of the Pacific convergence zones, with above normal air temperature and precipitation over the subtropical Pacific, and opposite conditions along the equator. By the next year (Year O) of the Warm Event, these anomalies have the opposite sign. It appears that enhanced convection and low surface pressure within the Pacific convergence zones contribute to the observed westerly wind anomalies in the western equatorial Pacific at the end of the Year -1, which are in turn tied to the onset of above normal equatorial SST in the following year. -from Authors