Teleconnections in the Southern Hemisphere

Abstract

Teleconnections are calculated from monthly mean anomalies of sea level pressure and 500 mb geopotential height for the Southern Hemisphere (10–90°S) for five-month winter and summer seasons. The monthly means were calculated from Australian analyses for the period from June 1972 to November 1980. Zonally averaged anomalies at both sea level and 500 mb display an out-of-phase relation between low and high latitudes and in midlatitudes are negatively correlated with anomalies in the subtropics and polar regions. In winter a striking zonal wavenumber 3 pattern is found over the Southern Ocean. Anomalies in 500 mb geopotential heights at (50°S, 95°E), (58°S, 150°W) and (38°S, 15°W) exhibit strong positive correlations while showing weaker negative correlations with heights over Antarctica and in low latitudes. A similar pattern appears in sea level pressure. In summer anomalies in 500 mb geopotential height over the three subtropical continents appear to occur out of phase with anomalies over the subtropical oceans and in a zonal wavenumber 3 pattern over the Southern Ocean near 55°S. Much of the pattern appears largely associated with low-frequency variability. A similar pattern with weaker correlations appears in sea level pressure in summer. The strongest teleconnection pattern in summertime sea level pressure features a strong negative correlation between the eastern Indian Ocean northwest of Australia and the subtropical eastern Pacific near Tahiti, which strongly resembles the pattern associated with the Southern Oscillation. The above features are well-reproduced in both halves of the period and in station data. The features found at 500 mb also appear in patterns obtained from eigenvector analysis.