Iwakiri et al. (2026) ENSO Recharge Oscillator Theory Integrating the Southward Wind Shift

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Geophysical Research Letters
• Year: 2026
• Date: 2026-04-10
• Authors: Tomoki Iwakiri, Malte F. Stuecker, Fei‐Fei Jin, Sen Zhao
• DOI: 10.1029/2025gl121295

Research Groups

Not specified in the abstract.

Short Summary

This study derives a new form of the Recharge Oscillator (RO) theory for ENSO that explicitly incorporates the seasonal migration of equatorial zonal wind anomalies. The new theory demonstrates how Bjerknes feedback depends on the central latitude of these wind anomalies and shows that a stochastic RO simulation can reproduce key ENSO characteristics like seasonal synchronization and combination tones.

Objective

• To derive a new form of the Recharge Oscillator (RO) theory under the low-frequency limit that explicitly incorporates the seasonal migration of equatorial zonal wind anomalies.

Study Configuration

• Spatial Scale: Equatorial Pacific region.
• Temporal Scale: Seasonal to interannual (low-frequency limit, boreal winter, seasonal migration, ENSO).

Methodology and Data

• Models used: Recharge Oscillator (RO) theory, stochastic RO simulation.
• Data sources: Not explicitly mentioned for this study's methodology; the paper focuses on theoretical derivation and simulation.

Main Results

• A new form of the Recharge Oscillator (RO) theory was derived, incorporating the seasonal migration of equatorial zonal wind anomalies.
• The Bjerknes feedback mechanism is shown to depend on the central latitude of zonal wind anomalies, decaying exponentially as winds shift away from the equator.
• Zonal wind anomalies centered off the equator induce equatorial wave adjustment, leading to a delayed effect on sea surface temperature anomalies.
• A stochastic RO simulation, incorporating a prescribed wind shift, reproduces approximately half the amplitude of observed ENSO seasonal synchronization.
• The simulation also successfully reproduces ENSO combination tones.

Contributions

• Provides the first explicit description of the effect of seasonal migration of equatorial zonal wind anomalies within the widely used Recharge Oscillator framework for ENSO.
• Offers a theoretical explanation for how the Bjerknes feedback and equatorial wave adjustment are modified by the latitudinal shift of wind anomalies.
• Demonstrates the capability of this modified RO theory to simulate observed ENSO characteristics, including seasonal synchronization and combination tones, thereby enhancing the conceptual understanding of ENSO physics.

Funding

Not specified in the abstract.

Citation

@article{Iwakiri2026ENSO,
  author = {Iwakiri, Tomoki and Stuecker, Malte F. and Jin, Fei‐Fei and Zhao, Sen},
  title = {ENSO Recharge Oscillator Theory Integrating the Southward Wind Shift},
  journal = {Geophysical Research Letters},
  year = {2026},
  doi = {10.1029/2025gl121295},
  url = {https://doi.org/10.1029/2025gl121295}
}