Nguyen et al. (2026) The CMIP6-downscaled CORDEX-Southeast Asia (SEA) ensemble: evaluation and benchmarking for megacities of SEA

Identification

• Journal: Geoscientific model development
• Year: 2026
• Date: 2026-08-19
• Authors: Phuong Loan Nguyen, Lisa V. Alexander, Thanh Ngo‐Duc, Faye Cruz, Jerasorn Santisirisomboon, Liew Juneng, Donaldi Sukma Permana, Jing Xiang Chung, Julie Mae B. Dado, John L. McGregor, Grace Redmond, Tse Wai Po, Fredolin Tangang, Tan Phan-Van, Son C. H. Truong, Marcus Thatcher, Long Trinh-Tuan, Ummu Ma’rufah, Jennifer Tibay, Giovanni Di Virgilio, Stephen White
• DOI: 10.5194/gmd-19-7653-2026

Research Groups

• Climate Change Research Centre, UNSW Sydney, New South Wales, Australia
• ARC Centre of Excellence for the Weather of the 21st Century, UNSW Sydney, Sydney, New South Wales, Australia
• Department of Space and Earth Sciences, University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, Hanoi, Vietnam
• Manila Observatory, Ateneo de Manila University campus, Quezon City, Philippines
• Ramkhamhaeng University Center of Regional Climate Change and Renewable Energy (RU-CORE), Bangkok, Thailand
• Department of Earth and Environmental Sciences, Faculty of Science and Technology, University Kebangsaan Malaysia, Bangi, Selangor, Malaysia
• Indonesia Agency of Meteorology, Climatology, and Geophysics (BMKG), Jakarta, Indonesia
• Faculty of Science and Marine Environment, University Malaysia Terengganu, Kuala Nerus, Terengganan, Malaysia
• The Commonwealth Scientific and Industrial Research Organisation, Melbourne, Victoria, Australia
• Met Office Hadley Centre, Exeter, United Kingdom (UK)
• Hong Kong Observatory, Hong Kong
• Department of Earth and Environmental Sciences, Faculty of Science and Technology, University Kebangsaan Malaysia, Bangi, Selangor, Malaysia
• Faculty of Meteorology, Hydrology, and Oceanography, University of Science, Vietnam National University, Hanoi, Vietnam
• The Commonwealth Scientific and Industrial Research Organisation, Melbourne, Victoria, Australia
• Climate Change Research Centre, UNSW Sydney, New South Wales, Australia
• Climate & Atmospheric Science, NSW Department of Climate Change, Energy, the Environment and Water, Sydney, New South Wales, Australia

Short Summary

This study evaluates the performance of a 21-member ensemble of regional climate simulations for Southeast Asia (SEA) generated by dynamically downscaling Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Models (GCMs). The ensemble captures the spatial and seasonal rainfall distribution reasonably well but tends to substantially overestimate observed rainfall.

Objective

• Evaluate the ability of CMIP6 CORDEX-SEA simulations in reproducing historical climate characteristics for Southeast Asia.
• Benchmark the performance of the CMIP6 CORDEX-SEA ensemble using a standardised benchmarking framework (BMF) developed by Isphording et al. (2024).

Study Configuration

• Spatial Scale: The study focuses on Southeast Asia, with an expanded domain that fully covers Myanmar (17.3° S–31.9° N, 86.5–149.3° E).
• Temporal Scale: The analysis is conducted for the period 1982–2014, with overlapping coverage of multiple observations and simulations.

Methodology and Data

• Models used: Three regional climate models (RCMs) were used: RegCM4-NH, CCAM, and HadREM3-GA7.05.
• Data sources: The study uses multiple global and regional gridded observational datasets to account for observational uncertainties in model evaluation.

Main Results

• The CMIP6 CORDEX-SEA ensemble captures the spatial and seasonal rainfall distribution reasonably well but tends to substantially overestimate observed rainfall.
• Wet biases are regionally and seasonally heterogeneous, with larger wet biases over monsoon-dominated regions and seasons (e.g., MC during November–April and the Mainland during May–October).
• All RCMs show widespread, statistically significant cold biases in daily mean temperature.

Contributions

• This study provides a comprehensive cross-ensemble evaluation of CMIP6 CORDEX-SEA simulations.
• The results highlight the importance of selecting suitable RCMs for downscaling activities within the CORDEX-SEA domain.

Funding

• This research was supported by the Asia-Pacific Network for Global Change Research (APN) under the SEACLID/CORDEX-SEA framework.

Citation

@article{Nguyen2026CMIP6downscaled,
  author = {Nguyen, Phuong Loan and Alexander, Lisa V. and Ngo‐Duc, Thanh and Cruz, Faye and Santisirisomboon, Jerasorn and Juneng, Liew and Permana, Donaldi Sukma and Chung, Jing Xiang and Dado, Julie Mae B. and McGregor, John L. and Redmond, Grace and Po, Tse Wai and Tangang, Fredolin and Phan-Van, Tan and Truong, Son C. H. and Thatcher, Marcus and Trinh-Tuan, Long and Ma’rufah, Ummu and Tibay, Jennifer and Virgilio, Giovanni Di and White, Stephen},
  title = {The CMIP6-downscaled CORDEX-Southeast Asia (SEA) ensemble: evaluation and benchmarking for megacities of SEA},
  journal = {Geoscientific model development},
  year = {2026},
  doi = {10.5194/gmd-19-7653-2026},
  url = {https://doi.org/10.5194/gmd-19-7653-2026}
}