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<p>This study evaluates the ability of 33 models from the phase 6 of the Coupled Model Intercomparison Project (CMIP6), to reproduce the precursory relation between the Indian Ocean Dipole (IOD) and the following year El Niño-Southern Oscillation (ENSO) (delayed IOD-ENSO relationship), and identify the sources of models’ uncertainty. The analysis is based on historical simulations from 1980 to 2014. While the multi-model ensemble mean generally captures the delayed IOD-ENSO linkage, a large inter-model divergence emerges in representing this relationship across the CMIP6 models. This diversity is attributable to inter-model spread in simulating IOD amplitude and the fidelity of associated easterly wind anomalies over the equatorial Indian Ocean (IO). The models that reproduce an enhanced delayed IOD-ENSO relationship tend to simulate amplified amplitudes of IOD in year 0, which generates enhanced easterly wind anomalies over the equatorial IO and mechanically excites more pronounced eastward propagating Kelvin waves. Consequently, these models reproduce a stronger response of sea surface temperature in the tropical eastern-central Pacific. The situation is vice versa for the models reproducing weaker delayed IOD-ENSO relationship. Further analysis demonstrates that the discrepancy in sea surface temperature response can be largely attributed to the differences in the zonal advection and the mean meridional currents. The inter-model disparities in IOD strength are predominantly attributed to the Rossby wave response due to adiabatic subsidence during the developing summer phase and the associated coupled air-sea processes. This study offers new insights into the CMIP6 models’ diversity to simulate the IOD-ENSO relationship and suggests potential improvements.</p>

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Precursorship between the Indian Ocean dipole and the following year ENSO in the CMIP6 simulations

  • 期刊论文

  • 发表日期：

    2025年12月9日

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  • Yue Zhong,
  • Wenshi Lin,
  • Dongliang Yuan,
  • Tuantuan Zhang,
  • Song Yang,
  • Shuheng Lin,
  • Wei Yu,
  • Hanjie Fan

摘要

This study evaluates the ability of 33 models from the phase 6 of the Coupled Model Intercomparison Project (CMIP6), to reproduce the precursory relation between the Indian Ocean Dipole (IOD) and the following year El Niño-Southern Oscillation (ENSO) (delayed IOD-ENSO relationship), and identify the sources of models’ uncertainty. The analysis is based on historical simulations from 1980 to 2014. While the multi-model ensemble mean generally captures the delayed IOD-ENSO linkage, a large inter-model divergence emerges in representing this relationship across the CMIP6 models. This diversity is attributable to inter-model spread in simulating IOD amplitude and the fidelity of associated easterly wind anomalies over the equatorial Indian Ocean (IO). The models that reproduce an enhanced delayed IOD-ENSO relationship tend to simulate amplified amplitudes of IOD in year 0, which generates enhanced easterly wind anomalies over the equatorial IO and mechanically excites more pronounced eastward propagating Kelvin waves. Consequently, these models reproduce a stronger response of sea surface temperature in the tropical eastern-central Pacific. The situation is vice versa for the models reproducing weaker delayed IOD-ENSO relationship. Further analysis demonstrates that the discrepancy in sea surface temperature response can be largely attributed to the differences in the zonal advection and the mean meridional currents. The inter-model disparities in IOD strength are predominantly attributed to the Rossby wave response due to adiabatic subsidence during the developing summer phase and the associated coupled air-sea processes. This study offers new insights into the CMIP6 models’ diversity to simulate the IOD-ENSO relationship and suggests potential improvements.