Hunt et al. (2025) Wetter, Weaker, and More Frequent Monsoon Low Pressure Systems in CMIP6 Future Scenarios

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

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-11-11
• Authors: Kieran M. R. Hunt, Andrew G. Turner
• DOI: 10.1175/jcli-d-25-0389.1

Research Groups

Not available from the abstract.

Short Summary

This study synthesizes future characteristics of South Asian monsoon low pressure systems (LPSs) using CMIP6 models, projecting that LPSs will become more frequent and deliver increased precipitation per event despite dynamic weakening, leading to an expanded risk of extreme rainfall and flooding deeper into the Indian subcontinent.

Objective

• To provide a robust synthesis of future characteristics of synoptic-scale low pressure systems (LPSs) influencing the South Asian monsoon under increasing global warming levels.

Study Configuration

• Spatial Scale: South Asian monsoon region, including the Bay of Bengal and the Indian subcontinent, with a focus on inland penetration and western parts of India.
• Temporal Scale: Future monsoons under increasing global warming levels, specifically between 1.5 °C and 2 °C of warming.

Methodology and Data

• Models used: 13 models from the Coupled Model Intercomparison Project phase 6 (CMIP6).
• Data sources: Reanalysis benchmarks (for model performance evaluation), CMIP6 model outputs. A novel, multicomponent skill score (FLIP: frequency, location, intensity, and precipitation) was developed and used to evaluate and weight model performance. Unsupervised clustering was employed for a storyline approach to deconstruct intermodel uncertainty.

Main Results

• Low pressure systems (LPSs) are projected to become more frequent as global warming levels increase.
• LPSs are projected to become dynamically weaker in terms of low-level vorticity.
• Per-LPS precipitation is projected to increase, with a super Clausius–Clapeyron scaling for the most intense storms, despite a general weakening of their circulation.
• This paradox is attributed to a projected increase in the background meridional moisture gradient and a structural change where boundary layer winds weaken less than those in the free troposphere, maintaining strong frictional moisture convergence.
• LPSs are projected to penetrate deeper inland, with a significant increase in post-landfall duration between 1.5 °C and 2 °C of warming.
• A storyline approach revealed four distinct future pathways for LPS changes; for example, a storyline with enhanced easterlies over Southeast Asia leads to a 36% increase in LPS frequency.
• The consistent outcome across diverse futures is a monsoon dominated by more numerous and wetter LPSs that track deeper into the subcontinent, expanding the risk of extreme rainfall and flooding to western parts of India.

Contributions

• Provides a robust, multi-model synthesis of future South Asian monsoon LPS characteristics using CMIP6 models.
• Introduces a novel, multicomponent skill score (FLIP) for evaluating and weighting model performance in simulating LPSs.
• Identifies and explains the paradox of increased per-LPS precipitation despite weaker circulation, attributing it to changes in moisture gradients and boundary layer wind structure.
• Utilizes a storyline approach based on unsupervised clustering to effectively deconstruct and explain intermodel uncertainty in LPS projections.
• Highlights the expanded risk of extreme rainfall and flooding to western parts of India due to deeper inland penetration of more numerous and wetter LPSs.

Funding

Not available from the abstract.

Citation

@article{Hunt2025Wetter,
  author = {Hunt, Kieran M. R. and Turner, Andrew G.},
  title = {Wetter, Weaker, and More Frequent Monsoon Low Pressure Systems in CMIP6 Future Scenarios},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-25-0389.1},
  url = {https://doi.org/10.1175/jcli-d-25-0389.1}
}