The Influence of Recurrent Modes of Climate Variability on the Occurrence of Monthly Temperature Extremes over South America

Associations are quantified between extreme warm and cold temperature months over South America and four major recurrent modes of climate variability: (1) El Niño Southern Oscillation (ENSO), (2) Pacific Decadal Oscillation (PDO), (3) Atlantic Multidecadal Oscillation (AMO), and (4) Southern Annular Mode (SAM). ENSO exerts a strong influence on extreme temperature months along the northwest coast, with most extreme warm (cold) temperature months occurring during strong warm (cold) phase ENSO conditions. The PDO displays a broadly similar relationship but with a reduced magnitude of association, suggesting that it is not highly influential on temperature extremes as an independent mode. The AMO is most influential on extreme temperature months across northeastern Brazil with the mode’s positive and negative phases concurrent with warm and cold months respectively. The SAM has a significant influence on the occurrence of extreme temperature months over the southern tip of South America, but overall does not exhibit a strong relationship with monthly extreme temperatures. Other synoptic scale circulation anomalies that are independent of the SAM may play an influential role in driving extreme temperatures here. While these four climate modes exert a considerable influence on extreme temperature occurrence across some regions of South America, our results suggest other influences also likely play key roles in modulating temperature. To identify these mechanisms, we further investigate the role of atmospheric circulation in modulating temperature variability at regional scales.