Hassan et al. (2025) Advancing convection-permitting regional climate modeling for monsoon extremes in data-scarce, topographically complex regions of South Asia

Identification

• Journal: Atmospheric Research
• Year: 2025
• Date: 2025-09-16
• Authors: Mujtaba Hassan, Sagheer Abbas, Bilal Ahmad, Farrukh Chishtie, Umer Zeeshan Ijaz, Xiaogang Shi, Waheed Iqbal, Tariq Mahmood, Rashid Mahmood, Ima Fatima
• DOI: 10.1016/j.atmosres.2025.108486

Research Groups

• Department of Space Science, Institute of Space Technology, Islamabad, Pakistan
• Department of Hydraulic Engineering, School of Civil Engineering, Shandong University, Jinan, China
• Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, BC, Canada
• Peaceful Society, Science and Innovation Foundation, Vancouver, BC, Canada
• Environmental Omics lab, Advanced Research Centre (ARC), University of Glasgow, Scotland, UK
• School of Social & Environmental Sustainability, University of Glasgow, Dumfries, Scotland, UK
• The Rossby Centre, Swedish Meteorological and Hydrological Institute (SMHI), Norrk¨oping, Sweden
• Pakistan Meteorological Department, Islamabad, Pakistan
• Water Engineering and Management, Asian Institute of Technology, Pathumthani, Thailand
• Abdus Salam International Centre for Theoretical Physics (ICTP) (developer of RegCM5)

Short Summary

This study evaluates the convection-permitting RegCM5 model's performance in simulating extreme monsoon precipitation events in data-scarce, topographically complex South Asia, demonstrating that the 3 km MOLOCH configuration significantly improves the accuracy of precipitation intensity, spatial distribution, and temporal variability compared to coarser hydrostatic simulations.

Objective

• To evaluate the performance of the Regional Climate Model RegCM5, specifically its convection-permitting configurations, in reproducing severe monsoon-driven extreme precipitation events in data-scarce, topographically complex regions of South Asia.

Study Configuration

• Spatial Scale: South Asia, with simulations conducted at 3 km (convection-permitting) and 12 km (hydrostatic) resolutions.
• Temporal Scale: Two severe monsoon-driven precipitation events: July 2010 and August 2022.

Methodology and Data

• Models used: Regional Climate Model RegCM5 (developed by ICTP) with:
  • Convection-permitting (3 km) non-hydrostatic cores: MOLOCH and MM5.
  • Coarser hydrostatic (12 km) core: MM4 (employing parameterized convection).
• Data sources:
  • ERA5 reanalysis
  • ERA5-Land reanalysis
  • Satellite-based GPM precipitation
  • Gloh2 ensemble product
  • In-situ observations

Main Results

• The 3 km MOLOCH configuration of RegCM5 significantly improved the simulation of precipitation intensity, spatial distribution, and temporal variability compared to 12 km hydrostatic runs.
• RegCM5-MOLOCH effectively captured 500 hPa geopotential height patterns associated with the 2010 Russian blocking ridge, resolving key synoptic drivers.
• The model successfully reproduced large-scale moisture transport and terrain-induced convergence along the Sulaiman mountain ranges.
• Diagnostics of Moisture Flux Convergence (MFC) and Integrated Vapor Transport (IVT) revealed strong southwesterly moisture inflow from the Arabian Sea converging over Sindh and Balochistan during August 2022, consistent with flood-affected areas.
• Spearman rank correlation analysis indicated robust linkages between simulated precipitation and sea surface temperature-related changes in La Niña and the Indian Ocean Dipole (IOD).
• While convection-permitting simulations generally reduced biases, some persistent wet biases remained, likely due to unresolved uncertainties in cloud microphysics, land–atmosphere coupling, and moisture transport.

Contributions

• Advances convection-permitting regional climate modeling (RegCM5-MOLOCH) for monsoon extremes in data-scarce, topographically complex regions of South Asia.
• Demonstrates the superior performance of 3 km non-hydrostatic configurations over coarser hydrostatic ones for simulating extreme precipitation events.
• Highlights the model's capability to resolve key synoptic drivers (e.g., 500 hPa geopotential height patterns, Russian blocking ridge) and terrain-induced convergence.
• Provides insights into the linkages between simulated precipitation and large-scale ocean-atmosphere modes (La Niña, IOD).
• Enhances the application of high-resolution regional modeling for improved flood risk assessment, early warning systems, and climate adaptation strategies in monsoon-affected regions.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Hassan2025Advancing,
  author = {Hassan, Mujtaba and Abbas, Sagheer and Ahmad, Bilal and Chishtie, Farrukh and Ijaz, Umer Zeeshan and Shi, Xiaogang and Iqbal, Waheed and Mahmood, Tariq and Mahmood, Rashid and Fatima, Ima},
  title = {Advancing convection-permitting regional climate modeling for monsoon extremes in data-scarce, topographically complex regions of South Asia},
  journal = {Atmospheric Research},
  year = {2025},
  doi = {10.1016/j.atmosres.2025.108486},
  url = {https://doi.org/10.1016/j.atmosres.2025.108486}
}