Increased longitudinal separation of equatorial rainfall responses to Eastern Pacific and Central Pacific El Niño under global warming

Abstract

El Niño induced equatorial precipitation centers shift to different longitudinal positions during Eastern Pacific (EP) and Central Pacific (CP) El Niño events, resulting in distinct global climate responses. However, it remains unexplored how EP and CP El Niño forced precipitation changes may differ under global warming. Here, we find that the longitudinal separation of precipitation centers in EP and CP El Niño events is projected to increase under global warming. Specifically, the precipitation anomalies during EP El Niño events will shift further eastward, while those during CP El Niño will intensify in their original positions. This change is attributed to the amplified equatorial thermocline feedback as the mean thermocline shoals. A more meridionally confined El Niño structure under global warming generates extra boundary layer moisture convergence in situ. This intensifies the precipitation anomalies in CP El Niño but shifts the precipitation center eastward towards the maximum sea surface temperature anomaly center in EP El Niño. The projected increased longitudinal separation of precipitation centers suggests that the differences in global climate impacts between EP and CP El Niño events will intensify under global warming.