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<p>The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual climate variability, with widespread global impacts. Using statistical and dynamical approaches, this study evaluates the performance of climate models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) in simulating ENSO diversity. Most models fail to capture observed El Niño asymmetry, with nearly 45% unable to simulate any extreme El Niño events. Using a reduced-complexity conceptual model, we trace this deficiency to weakened or absent westerly wind bursts (WWBs), which are critical atmospheric triggers for extreme El Niño development. Our experiments demonstrate that (a) WWBs in climate models are too weak to initiate and amplify strong El Niño events, and (b) cold sea surface temperature biases in the central Pacific suppress WWB activity by raising the threshold for convective triggering. These mean-state biases also shift the location and weaken the strength of the Bjerknes feedback. Improving WWB representation and central Pacific SST seasonality is essential for realistic ENSO simulation and more reliable projections under climate change.</p>

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Linking mean-state biases to ENSO diversity in climate models: the key role of westerly wind burst suppression

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Gobinda Manna,
  • S. Sandeep,
  • Nan Chen

摘要

The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual climate variability, with widespread global impacts. Using statistical and dynamical approaches, this study evaluates the performance of climate models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) in simulating ENSO diversity. Most models fail to capture observed El Niño asymmetry, with nearly 45% unable to simulate any extreme El Niño events. Using a reduced-complexity conceptual model, we trace this deficiency to weakened or absent westerly wind bursts (WWBs), which are critical atmospheric triggers for extreme El Niño development. Our experiments demonstrate that (a) WWBs in climate models are too weak to initiate and amplify strong El Niño events, and (b) cold sea surface temperature biases in the central Pacific suppress WWB activity by raising the threshold for convective triggering. These mean-state biases also shift the location and weaken the strength of the Bjerknes feedback. Improving WWB representation and central Pacific SST seasonality is essential for realistic ENSO simulation and more reliable projections under climate change.