On the Spatiotemporal Diversity of Atlantic Nino and Associated Rainfall Variability Over West Africa and South America

The spatiotemporal evolutions of equatorial Atlantic sea surface temperature anomalies (SSTAs) during Atlantic Nino events and the associated climate impacts on the surrounding continents are extremely diverse. In this study, we construct longitude-time maps of equatorial Atlantic SSTAs for each observed Atlantic Nino event during 1948-2019 and perform a spatiotemporal empirical orthogonal function analysis to identify the four most frequently recurring Atlantic Nino varieties. The first two contrast the timing of dissipation (early terminating vs. persistent) and the other two the timing of onset (early onset vs. late onset). Largely consistent with the differences in the timings of onset and dissipation, these four varieties display remarkable differences in rainfall response over West Africa and South America. Most of the varieties are subject to onset mechanisms that involve preconditioning in boreal spring by either the Atlantic meridional mode or Pacific El Nino, while for the late onset variability there is no clear source of external forcing.