资源环境科技发展态势分析平台

The influence of El Nino-Southern Oscillation (ENSO) on the Atlantic Nino over the past 113 years is investigated by comparing multi-year and single-year ENSO events. Multi-year ENSO events sustain an anomalous zonal gradient of sea surface temperature (SST) in the equatorial western to central Pacific even during boreal spring and summer. This SST gradient is coupled with an anomalous Walker circulation and atmospheric deep convection through the Bjerknes feedback. During multi-year La Ninas, for example, a strengthened Pacific Walker circulation extends into the tropical Atlantic in boreal spring, a season when both the Pacific and Atlantic intertropical convergence zones become more symmetric about the equator. As a result, surface westerly wind anomalies appear over the equatorial Atlantic, triggering an Atlantic Nino. By contrast, such a teleconnection is not found in the spring following the peak of single-year ENSO events. A Pacific pacemaker model experiment reproduces the observed atmospheric response and its impact on the Atlantic Nino, further supporting the importance of prolonged ENSO forcing. The contrasting influence of multi-year and single-year events explains the fragile relationship between ENSO and the Atlantic Nino. An empirical orthogonal function (EOF) analysis shows that the leading EOF mode (EOF-1) for the spring tropical western to central Pacific SST anomalies captures the characteristics of multi-year ENSO events. EOF-1 is highly correlated with the summer Atlantic Nino over the past 113 years while the Nino-3 SST is not. These correlations indicate that ocean-atmosphere coupling in the equatorial western to central Pacific plays a major role in shaping ENSO teleconnections in boreal spring.