Comparing the Linkage between Springtime Central Pacific Cross-Equatorial Winds and Wintertime ENSO Events in Reanalyses and CMIP6 Models

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Abstract Recent studies highlighted the springtime cross-equatorial meridional wind anomaly over the central Pacific as an important precursor to El Niño–Southern Oscillation (ENSO) events in the following winter, primarily through atmosphere–ocean interactions such as the wind–evaporation–sea surface temperature (SST) feedback. The cross-equatorial wind leads ENSO events by 8 months in reanalysis datasets, with the correlation coefficient of up to 0.63. Here, we assess the fidelity of this relationship in climate models from the Coupled Model Intercomparison Project phase 6 (CMIP6). Our analysis reveals that all CMIP6 models substantially underestimate this relationship. Further investigation suggests that this deficiency is largely due to the overestimation of ENSO persistence in models, as evidenced by the elevated autocorrelation between springtime and wintertime ENSO indices. In reanalyses, the springtime cross-equatorial wind anomaly over the central Pacific often coincides with a cold SST anomaly in the cold tongue but precedes a warm SST anomaly in the following winter. Most CMIP6 models overestimate the autocorrelation between springtime and wintertime ENSO events, which overshadows the “springtime wind–wintertime ENSO” relationship. However, upon removing the springtime ENSO signal from the analysis, most models successfully reproduce a strong linkage between springtime cross-equatorial winds and subsequent ENSO events. These findings reaffirm the critical role of springtime meridional wind anomalies in shaping ENSO evolution and offer valuable insights for correcting model biases and improving model performance in simulating ENSO dynamics and predictability.

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