Toride et al. (2025) Roles of MJO and Tropical–Extratropical Interactions in Subseasonal Conditions Related to Landfalling Atmospheric Rivers

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

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-12-11
• Authors: Kinya Toride, Gregory J. Hakim, Andrew Hoell
• DOI: 10.1175/jcli-d-25-0211.1

Research Groups

Not specified in the provided abstract.

Short Summary

This study investigates the role of the Madden–Julian oscillation (MJO) and other tropical–extratropical interactions in generating landfalling atmospheric rivers (ARs) over the West Coast of North America. It finds that weakly coupled tropical–extratropical interactions are the primary drivers of AR activity, with the MJO contributing only a minor role, mainly to subtropical vapor transport for Alaska ARs.

Objective

• To investigate the role of the Madden–Julian oscillation (MJO) and other tropical–extratropical interactions in generating atmospheric rivers (ARs) using a linear inverse model (LIM) framework.
• To examine subseasonal conditions that preferentially lead to landfalling ARs over Alaska, the Pacific Northwest, and California during boreal winters.

Study Configuration

• Spatial Scale: Tropics, Extratropics, Alaska, Pacific Northwest (PNW), California (West Coast of North America).
• Temporal Scale: Boreal winters, subseasonal (10–30 days), 14-day window (for composite analysis).

Methodology and Data

• Models used: Linear Inverse Model (LIM) framework.
• Data sources: Not specified in the provided abstract.

Main Results

• Prolonged AR active conditions (14-day window) are primarily driven by weakly coupled modes, with small contributions from tropically driven modes.
• The only significant signal from tropical heating modes (MJO) is the subtropical vapor transport associated with MJO phases 6–7 for Alaska ARs.
• For all regions, the evolving optimal initial conditions for AR patterns show nearly stationary phase patterns but propagating wave activity that shifts the location of maximum amplitude in time.
• The MJO partially contributes to the linear predictable growth of AR patterns, while weakly coupled modes remain the main drivers.
• The MJO and weakly coupled modes constructively interfere in subtropical vapor transport and destructively interfere in tropical convective activity.
• The MJO's contribution to subseasonal AR predictions is relatively minor compared to other weakly coupled tropical–extratropical interactions.

Contributions

• Underscores the critical importance of accurately resolving weakly coupled tropical–extratropical interactions to improve subseasonal AR predictions.
• Challenges the common assumption that the MJO is a major driver for subseasonal AR prediction, demonstrating its relatively minor role compared to other weakly coupled processes.
• Provides a detailed analysis of the interplay (constructive and destructive interference) between MJO and weakly coupled modes in different atmospheric processes.

Funding

Not specified in the provided abstract.

Citation

@article{Toride2025Roles,
  author = {Toride, Kinya and Hakim, Gregory J. and Hoell, Andrew},
  title = {Roles of MJO and Tropical–Extratropical Interactions in Subseasonal Conditions Related to Landfalling Atmospheric Rivers},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-25-0211.1},
  url = {https://doi.org/10.1175/jcli-d-25-0211.1}
}