Interpretation and Implications of the Observed Inter–El Niño Variability

Abstract

The variability in extratropical atmospheric anomalies from one El Niño winter to another is examined. This study offers an interpretation for such observed inter–El Niño variations and discusses implications for seasonal atmospheric predictability. The seven strongest El Niño events of the 1950–94 period are selected in order to form a composite 500-mb circulation anomaly over the Pacific–North American region. Individual events are shown to deviate significantly from such a composite. Using a large ensemble of atmospheric general circulation model simulations forced with the observed sea surface temperatures of 1950–94, the authors argue that the observed inter–El Niño atmospheric variations are primarily due to internal atmospheric variability. The observed inter–El Niño variability in spatial patterns of the extratropical circulation anomalies appears not to be a deterministic feature of the SSTs and may thus be inherently unpredictable. Atmospheric general circulation model results further s... Abstract The variability in extratropical atmospheric anomalies from one El Niño winter to another is examined. This study offers an interpretation for such observed inter–El Niño variations and discusses implications for seasonal atmospheric predictability. The seven strongest El Niño events of the 1950–94 period are selected in order to form a composite 500-mb circulation anomaly over the Pacific–North American region. Individual events are shown to deviate significantly from such a composite. Using a large ensemble of atmospheric general circulation model simulations forced with the observed sea surface temperatures of 1950–94, the authors argue that the observed inter–El Niño atmospheric variations are primarily due to internal atmospheric variability. The observed inter–El Niño variability in spatial patterns of the extratropical circulation anomalies appears not to be a deterministic feature of the SSTs and may thus be inherently unpredictable. Atmospheric general circulation model results further s...