Neethu et al. (2025) A model-based assessment of the regional safe aerosol boundary for the South Asian monsoon region

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

Identification

• Journal: Environmental Research Letters
• Year: 2025
• Date: 2025-11-24
• Authors: C Neethu, Thejna Tharammal, Govindasamy Bala
• DOI: 10.1088/1748-9326/ae2345

Research Groups

[Information not available in the provided abstract.]

Short Summary

This study uses idealized climate model simulations to rigorously confirm proposed planetary boundary values for regional aerosol optical depth (AOD) in South Asia. It finds that an AOD of 0.25 can cause drought conditions (>10% precipitation reduction) in India, and an AOD of 0.5 reduces Indian summer monsoon precipitation by 19%.

Objective

• To rigorously confirm, using idealized climate model simulations, the proposed planetary boundary values for regional aerosol optical depth (AOD) in South Asia by analyzing the response of South Asian summer monsoon precipitation to increased AOD.

Study Configuration

• Spatial Scale: South Asia (SA), India, North Indian Ocean, Western Pacific Ocean
• Temporal Scale: South Asian summer monsoon

Methodology and Data

• Models used: Idealized climate model simulations
• Data sources: Modeled present-day aerosol optical depth (AOD) value (0.14) as a baseline for simulations.

Main Results

• A regional AOD of 0.25 leads to drought conditions in India, characterized by a mean precipitation reduction exceeding 10%.
• An AOD of 0.5 reduces Indian summer monsoon precipitation by approximately 19%.
• The reduction in summer monsoon precipitation is driven by both fast adjustments (rapid atmospheric response to aerosol radiative forcing) and slow responses (responses to changes in sea surface temperature).
• Rapid adjustments, primarily due to anthropogenic sulfates, involve enhanced atmospheric stability, subsidence, and suppressed cloud formation and precipitation.
• Slow responses involve zonal surface temperature gradients between the North Indian Ocean and Western Pacific Ocean, leading to changes in the Walker circulation, anomalous subsidence over South Asia, and decreased monsoon precipitation.
• Enhanced aerosol loading over South Asia reduces monsoon precipitation regardless of aerosol composition, though the magnitude of reduction depends on whether aerosols are primarily reflective or absorbing.

Contributions

• Provides the first rigorous model-based confirmation of proposed planetary boundary values for regional aerosol optical depth (AOD) in South Asia, addressing a critical research gap.
• Confirms the significant risk of major disruptions to regional hydrology in South Asia if regional aerosol loading exceeds the proposed boundary values.

Funding

[Information not available in the provided abstract.]

Citation

@article{Neethu2025modelbased,
  author = {Neethu, C and Tharammal, Thejna and Bala, Govindasamy},
  title = {A model-based assessment of the regional safe aerosol boundary for the South Asian monsoon region},
  journal = {Environmental Research Letters},
  year = {2025},
  doi = {10.1088/1748-9326/ae2345},
  url = {https://doi.org/10.1088/1748-9326/ae2345}
}