The equatorial Atlantic oscillation and its response to ENSO

An internal equatorial Atlantic oscillation has been identified by analyzin g sea surface temperature (SST) observations. The equatorial Atlantic oscil lation can be viewed as the Atlantic analogue of the El Nino/Southern Oscil lation (ENSO) phenomenon in the equatorial Pacific, but it is much less vig orous. The equatorial Atlantic oscillation is strongly influenced by the Pa cific ENSO with the equatorial Atlantic sea surface temperature lagging by about six months. This lag can be explained by the dynamical adjustment tim e of the equatorial Atlantic to low-frequency wind stress variations and th e seasonally varying background state, which favours strongest growth of pe rturbations in summer. Results of an extended-range simulation with a coupl ed ocean-atmosphere GCM support this picture.