Origin of the South Pacific Convergence Zone

Abstract

The importance of the presence of South America and Australia to the existence and orientation of the South Pacific Convergence Zone (SPCZ) during January is explored using the ECMWF T21 model. Each of the continents is removed from the model and replaced with an ocean surface, and the resulting precipitation and circulation associated with the SPCZ are then compared to a perpetual January control run. Results show that the presence of South America and the equatorial Pacific upwelling zone does not appear to be crucial to the SPCZ, but that the removal of Australia destroys the southern monsoon and substantially weakens the western part of the SPCZ. This suggests that the northwest-southeast orientation of the SPCZ during southern summer is more dependent on interactions with the midlatitude westerlies over the South Pacific than on the distribution of sea surface temperature and land over the Southern Hemisphere.