Impact of Winter Tropical Southern Atlantic Sea Surface Temperature on the Subsequent Evolution of ENSO

Using reanalysis and model simulation, this study identified an evident linkage between tropical southern Atlantic sea surface temperature anomalies (TSA‐SSTA) in winter and the following El Niño‐Southern Oscillation (ENSO) evolution, and investigated the possible mechanism. Results indicated a significant TSA‐ENSO lag relationship, where the anomalous warm (cold) TSA‐SSTA in preceding winter favors cold (warm) ENSO‐related SSTA in the following summer. The mechanism responsible for this TSA‐ENSO relation is detailed as follows. The anomalous warm TSA‐SST in preceding winter can sustain to the following summer, which then induces an anomalous Walker circulation spanning across the tropical Atlantic and Pacific. This anomalous Walker circulation triggers an anomalous low‐level easterly over the tropical Pacific that initiates the important air‐sea feedback. The zonal advection, Ekman pumping, and Bjerknes thermocline feedback, triggered by the anomalous warm TSA‐SST, are dominant processes within the oceanic mixing layer to facilitate the cold ENSO‐related SSTA. The anomalous cold TSA‐SST corresponds to the opposite circulation anomaly and SSTA. The validity of the mechanism can be further corroborated by numerical modeling. This study offers new findings regarding the linkage between tropical Pacific and tropical Atlantic and provides a potential new predictor for improving the accuracy of ENSO prediction, which is of great significance for addressing climate‐related risks.