Chen et al. (2025) Dynamic Changes in Quasi‐Biweekly Variability Drive Increased Extreme Rainfall and Whiplash Events Over Asian Monsoon Regions

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

Identification

• Journal: Geophysical Research Letters
• Year: 2025
• Date: 2025-12-17
• Authors: Hongli Chen, Pang‐Chi Hsu, Bo Lü, Jie Wu, Lijuan Chen, Yunyun Liu
• DOI: 10.1029/2025gl119215

Research Groups

Not explicitly mentioned in the abstract.

Short Summary

This study reveals a significant intensification of quasi-biweekly rainfall variability in the Asian monsoon region over the past four decades, primarily driven by dynamical changes in vertical velocity perturbations, with thermodynamic moisture increases playing a secondary role. Climate models project stronger future variability only when thermodynamic moistening outweighs dynamical uncertainty, highlighting the need for improved model representation of this circulation.

Objective

• To investigate the drivers behind the observed intensification of quasi-biweekly rainfall variability in the Asian monsoon region and its representation and projection in climate models.

Study Configuration

• Spatial Scale: Asian monsoon region, specifically southern China, the northern Bay of Bengal, and northwestern South Asia.
• Temporal Scale: Past four decades (recent two decades relative to the earlier two), historical simulations, and future scenarios.

Methodology and Data

• Models used: CMIP6 and CESM2-LENS (for historical simulations and future scenarios).
• Data sources: Multiple reanalyses (for observed intensification).

Main Results

• Quasi-biweekly rainfall variability has intensified significantly over the past four decades in southern China, the northern Bay of Bengal, and northwestern South Asia.
• Regional quasi-biweekly rainfall variability increased by 12%–44% in the recent two decades compared to the earlier two, as indicated by multiple reanalyses.
• This intensification is primarily driven by dynamical changes in vertical velocity perturbations.
• Thermodynamic increases in mean moisture play a secondary role in this intensification.
• The strong dynamical influence accounts for much of the spread observed in historical simulations from CMIP6 and CESM2-LENS.
• Climate models consistently project stronger quasi-biweekly variability under future scenarios only when thermodynamic moistening outweighs the dynamical uncertainty.

Contributions

• Identifies the central role of quasi-biweekly circulation in monsoonal rainfall extremes.
• Quantifies the relative contributions of dynamical and thermodynamic factors to the intensification of quasi-biweekly rainfall variability.
• Highlights the critical need to improve the representation of quasi-biweekly variability in climate models for more accurate projections of future rainfall extremes.

Funding

Not explicitly mentioned in the abstract.

Citation

@article{Chen2025Dynamic,
  author = {Chen, Hongli and Hsu, Pang‐Chi and Lü, Bo and Wu, Jie and Chen, Lijuan and Liu, Yunyun},
  title = {Dynamic Changes in Quasi‐Biweekly Variability Drive Increased Extreme Rainfall and Whiplash Events Over Asian Monsoon Regions},
  journal = {Geophysical Research Letters},
  year = {2025},
  doi = {10.1029/2025gl119215},
  url = {https://doi.org/10.1029/2025gl119215}
}