On the interannual variability of African easterly waves and its relationship with El Niño-Southern Oscillation

African easterly waves (AEWs) have important impacts on rainfall, drought, and the development of tropical cyclones in the Atlantic basin. However, the interannual variability of AEWs and their near-environmental characteristics are still poorly understood. Using an object-oriented AEW tracker, this study investigates the interannual variability of AEW characteristics and its association with El Niño–Southern Oscillation (ENSO) and Atlantic tropical cyclone activity. The variability of tracked AEW characteristics was found to be largely comparable across two reanalysis datasets, suggesting these fields are reliable indicators of AEW activity. ENSO is shown to impact AEW strength, moisture content, convective activity, and vertical structure on interannual time scales. Supporting this finding is an inverse correlation between these wave attributes and the oceanic Niño index, as well as vertical composites indicating an enhancement of these attributes during La Niña years versus El Niño years. Additionally, the ENSO–AEW relationship is mostly confined to the African continent. It is hypothesized that ENSO influences AEW activity through the modification of regional circulations including the tropical easterly jet, the African easterly jet, and the West African monsoon. These circulations are stronger and displaced during La Niña years, potentially increasing convection in the vicinity of AEWs and enhancing thermodynamic instabilities. Additionally, differences in AEW characteristics between active and inactive Atlantic tropical cyclone years are similar to the differences found between ENSO phases. Overall, these findings demonstrate that the ENSO–AEW relationship is a distinct teleconnection that may have important impacts on local weather and downstream tropical cyclogenesis.