Winter sea surface temperature interhemispheric dipole as a predictor for Sahel summer rainfall

Abstract Skillful prediction of Sahel summer rainfall (SSR) is critical for mitigating hydrometeorological disasters in this vulnerable climate hotspot. In this study, we employ observational analysis from 1950–2023 to show that the sea surface temperature interhemispheric dipole in winter (SSTIDw) has a strong influence on SSR. A positive SSTIDw anomaly-marked by relatively warmer Northern Hemisphere sea surface temperatures-persists through spring to summer and leads to persistent negative surface pressure anomalies and anomalous cyclonic circulation. This intensifies the Saharan heat low and reinforces anomalous westerly and southwesterly flows across the Atlantic and the Guinea Coast, enhancing moisture flux convergence and rainfall in the Sahel. Based on this relationship, we develop an SSTIDw-based linear regression model that skillfully captures SSR characteristics. These findings highlight the multi-month lead time predictability of SSR, which is critical for climate-informed decision making in the Sahel.