Preprints
https://doi.org/10.5194/egusphere-2024-3770
https://doi.org/10.5194/egusphere-2024-3770
10 Feb 2025
 | 10 Feb 2025

Calibrating the GAMIL3-1° climate model using a derivative-free optimization method

Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, and Wenjie Dong

Abstract. Parameterization in climate models often involves parameters that are poorly constrained by observations or theoretical understanding alone. Manual tuning by experts can be time-consuming, subjective, and prone to underestimating uncertainties. Automated tuning methods offer a promising alternative, enabling faster, objective improvements in model performance and better uncertainty quantification. This study presents an automated parameter-tuning framework that employs a derivative-free optimization solver (DFO-LS) to simultaneously perturb and tune multiple convection-related and microphysics parameters. The framework explicitly accounts for observational and initial condition uncertainties (internal variability) to calibrate a 1-degree resolution atmospheric model (GAMIL3). Two experiments, adjusting 10 and 20 parameters, were conducted alongside three sensitivity experiments that varied initial parameter values for a 10-parameter case. Both of the first two experiments showed a rapid decrease in the cost function, with the 10-parameter optimization significantly improving model accuracy in 24 out of 34 variables. Expanding to 20 parameters further enhanced accuracy, with improvement in 25 of 34 variables, though some structural model errors emerged. Ten-year AMIP simulations validated the robustness and stability of the tuning results, showing that the improvements persisted over extended simulations. Additionally, evaluations of the coupled model with optimized parameters showed–compare to the default parameter setting–reduced climate drift, a more stable climate system, and more realistic sea surface temperatures, despite a slight energy imbalance and some regional biases. The sensitivity experiments underscored the efficiency of the tuning algorithm and highlight the importance of expert judgment in selecting initial parameter values. This tuning framework is broadly applicable to other general circulation models (GCMs), supporting comprehensive parameter tuning and advancing model development.

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Journal article(s) based on this preprint

02 Dec 2025
Calibrating the GAMIL3-1° climate model using a derivative-free optimization method
Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, Wenjie Dong, and Junjie Huang
Geosci. Model Dev., 18, 9293–9318, https://doi.org/10.5194/gmd-18-9293-2025,https://doi.org/10.5194/gmd-18-9293-2025, 2025
Short summary
Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, and Wenjie Dong

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3770', Anonymous Referee #1, 21 Apr 2025
    • AC1: 'Reply on RC1', Wenjun Liang, 30 Jul 2025
  • RC2: 'Comment on egusphere-2024-3770', Anonymous Referee #2, 31 May 2025
    • AC2: 'Reply on RC2', Wenjun Liang, 30 Jul 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3770', Anonymous Referee #1, 21 Apr 2025
    • AC1: 'Reply on RC1', Wenjun Liang, 30 Jul 2025
  • RC2: 'Comment on egusphere-2024-3770', Anonymous Referee #2, 31 May 2025
    • AC2: 'Reply on RC2', Wenjun Liang, 30 Jul 2025

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload
AR by Wenjun Liang on behalf of the Authors (31 Jul 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (11 Aug 2025) by Tilo Ziehn
RR by Anonymous Referee #3 (24 Sep 2025)
RR by Anonymous Referee #2 (05 Oct 2025)
ED: Publish subject to minor revisions (review by editor) (20 Oct 2025) by Tilo Ziehn
AR by Wenjun Liang on behalf of the Authors (30 Oct 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (10 Nov 2025) by Tilo Ziehn
AR by Wenjun Liang on behalf of the Authors (10 Nov 2025)  Author's response   Manuscript 

Journal article(s) based on this preprint

02 Dec 2025
Calibrating the GAMIL3-1° climate model using a derivative-free optimization method
Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, Wenjie Dong, and Junjie Huang
Geosci. Model Dev., 18, 9293–9318, https://doi.org/10.5194/gmd-18-9293-2025,https://doi.org/10.5194/gmd-18-9293-2025, 2025
Short summary
Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, and Wenjie Dong

Data sets

Model Optimization Simon Tett and Wenjun Liang https://doi.org/10.5281/zenodo.14772250

Wenjun Liang, Simon Frederick Barnard Tett, Lijuan Li, Coralia Cartis, Danya Xu, and Wenjie Dong

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Short summary
Predicting climate accurately is challenging due to uncertainties in model parameters. This study introduced an automated approach to refine key parameters, focusing on processes like cloud formation and atmospheric circulation. Testing adjustments to 10 and 20 parameters improved the model’s accuracy and stability, reducing errors in long-term simulations. This faster, more reliable method enhances climate models, supporting better future predictions and aiding global decision-making.
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