Liu et al. (2026) Intraseasonal Northwest–Southeast Oscillation of the Tropical Easterly Jet Core and Its Modulation by Atmospheric Internal Dynamics and Boreal Summer Intraseasonal Oscillation

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Identification

• Journal: Journal of Climate
• Year: 2026
• Date: 2026-04-09
• Authors: Shihua Liu, Zhiping Wen, Xin Wang, Sihua Huang, Yanke Tan
• DOI: 10.1175/jcli-d-25-0372.1

Research Groups

Not specified in abstract.

Short Summary

This study identifies and explains a distinct northwest-southeast intraseasonal oscillation of the Tropical Easterly Jet (TEJ) core during boreal summer, revealing its primary governance by upper-tropospheric dynamic processes and modulation by the northward propagation of large-scale convective anomalies associated with the Boreal Summer Intraseasonal Oscillation (BSISO).

Objective

• To identify and understand the underlying dynamical mechanisms governing the intraseasonal variability of the Tropical Easterly Jet (TEJ) core position during boreal summer.

Study Configuration

• Spatial Scale: Upper troposphere, tropical Indian Ocean, southern Indian Peninsula.
• Temporal Scale: Boreal summer, intraseasonal variability (specifically linked to BSISO phases).

Methodology and Data

• Models used: Not specified in abstract.
• Data sources: Not specified in abstract; analysis includes vorticity budget analysis and examination of large-scale convective anomalies.

Main Results

• A distinct northwest–southeast (NW–SE) oscillation of the TEJ core is identified.
• This oscillation is closely linked to alternating cyclonic and anticyclonic anomalies over the tropical Indian Ocean, which modulate upper-tropospheric wind fields, inducing westerly (easterly) anomalies over the southern Indian Peninsula.
• A vorticity budget analysis reveals that the NW–SE oscillation is primarily governed by three dominant dynamic processes: planetary vorticity advection, horizontal advection of relative vorticity, and the tilting term.
• While primarily maintained by upper-tropospheric dynamic processes, the initiation of this intraseasonal oscillation is modulated by the northward propagation of large-scale convective anomalies associated with the Boreal Summer Intraseasonal Oscillation (BSISO).
• During BSISO phases 6–8 (2–4), the northward propagation of suppressed (enhanced) convection induces positive (negative) relative vorticity and associated westerly (easterly) anomalies in the upper troposphere over the northern Indian Ocean, promoting a northwestward (southeastward) displacement of the TEJ core roughly one phase later.

Contributions

• Improved understanding of the spatiotemporal variability of the TEJ core.
• Elucidation of the combined dynamical and thermodynamical controls governing the TEJ core's intraseasonal fluctuations.

Funding

Not specified in abstract.

Citation

@article{Liu2026Intraseasonal,
  author = {Liu, Shihua and Wen, Zhiping and Wang, Xin and Huang, Sihua and Tan, Yanke},
  title = {Intraseasonal Northwest–Southeast Oscillation of the Tropical Easterly Jet Core and Its Modulation by Atmospheric Internal Dynamics and Boreal Summer Intraseasonal Oscillation},
  journal = {Journal of Climate},
  year = {2026},
  doi = {10.1175/jcli-d-25-0372.1},
  url = {https://doi.org/10.1175/jcli-d-25-0372.1}
}