Stuivenvolt‐Allen et al. (2025) Atmospheric Nonlinearity Controls ENSO Asymmetry in a Hybrid Statistical‐Dynamical Climate Model

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

Identification

• Journal: Geophysical Research Letters
• Year: 2025
• Date: 2025-10-16
• Authors: Jacob Stuivenvolt‐Allen, Alexey V. Fedorov
• DOI: 10.1029/2025gl117456

Research Groups

Researchers associated with the Community Earth System Model (CESM) development and application.

Short Summary

This study investigates the causes of El Niño Southern Oscillation (ENSO) asymmetry, finding that while oceanic nonlinearities would lead to stronger La Niñas, the observed asymmetry (stronger El Niños) is critically dependent on nonlinear atmospheric wind-stress responses to sea surface temperature anomalies.

Objective

• To understand the roles of oceanic and atmospheric nonlinearities in the asymmetry of El Niño Southern Oscillation (ENSO) phases.

Study Configuration

• Spatial Scale: Eastern equatorial Pacific
• Temporal Scale: Interannual (ENSO phases)

Methodology and Data

• Models used: Hybrid statistical-dynamical model based on the Community Earth System Model version 2 (CESM2), coupling the CESM2 ocean component with a partially statistical atmospheric component.
• Data sources: Observational data for wind-stress nonlinearities (implied by "observed wind-stress nonlinearities").

Main Results

• Without the nonlinear atmospheric wind-stress response to sea surface temperature (SST) anomalies, the model exhibits stronger La Niñas than El Niños and negative skewness, contrary to observations. This is attributed to oceanic nonlinearities.
• Only by incorporating the observed wind-stress nonlinearities can the model reproduce the observed ENSO asymmetry (positive skewness of SST variations, stronger El Niños).
• The atmosphere's critical role in establishing the observed ENSO asymmetry is highlighted within this framework.

Contributions

• Demonstrates that atmospheric wind-stress nonlinearities are essential for reproducing the observed ENSO asymmetry, counteracting the effects of oceanic nonlinearities.
• Provides a clear distinction between the roles of oceanic and atmospheric nonlinearities in shaping ENSO characteristics.
• Offers a novel application of a hybrid statistical-dynamical model to disentangle complex climate feedback mechanisms.

Funding

Funding information is not provided in the abstract.

Citation

@article{StuivenvoltAllen2025Atmospheric,
  author = {Stuivenvolt‐Allen, Jacob and Fedorov, Alexey V.},
  title = {Atmospheric Nonlinearity Controls ENSO Asymmetry in a Hybrid Statistical‐Dynamical Climate Model},
  journal = {Geophysical Research Letters},
  year = {2025},
  doi = {10.1029/2025gl117456},
  url = {https://doi.org/10.1029/2025gl117456}
}