Yang et al. (2026) 20 years of trials and insights: bridging legacy and next generation in ParFlow and Land Surface Model Coupling

Identification

• Journal: Geoscientific model development
• Year: 2026
• Date: 2026-03-04
• Authors: Chao Yang, A Sun, Shupeng Zhang, YONGJIU DAI, Stefan Kollet, R. M. Maxwell
• DOI: 10.5194/gmd-19-1849-2026

Research Groups

• School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
• Institute of Bio- and Geosciences (IBG-3, Agrosphere), Forschungszentrum Jülich (FZJ), Jülich, Germany
• Center for High-Performance Scientific Computing in Terrestrial Systems (HPSC TerrSys), Geoverbund ABC/J, Jülich, Germany
• Department of Civil and Environmental Engineering, The High Meadows Environmental Institute and the Integrated GroundWater Modeling Center, Princeton University, Princeton, USA

Short Summary

This study reviews two decades of ParFlow-land/atmosphere coupled modeling, presents a renewed recoupling of ParFlow with the updated Common Land Model (CoLM) demonstrating improved performance, and proposes a sustainable coupling framework and a community-led model intercomparison project (PLCMIP) for future development.

Objective

• To review key findings from two decades of ParFlow–land/atmosphere coupled modeling efforts, highlighting groundwater–land–atmosphere interactions.
• To present a renewed recoupling of ParFlow with the updated water and energy modules of CoLM, demonstrating improved performance.
• To propose a modular and maintainable coupling framework for long-term sustainability and address functional extensibility, data/code interoperability, and parallel computing needs.
• To summarize existing ParFlow-based coupled systems and propose a community-led ParFlow-Land Surface Coupled Model Intercomparison Project (PLCMIP).

Study Configuration

• Spatial Scale: Regional scale over the North Pearl River Basin, China, approximately 242.35 km (x direction) × 140.41 km (y direction) × 103.43 m (z direction) with a horizontal resolution of approximately 1 km. Also, single-column synthetic cases for snow performance.
• Temporal Scale: Review of two decades (2005-2025) of coupled modeling efforts. Simulations for the real-world case used meteorological forcing for the year 2018. Synthetic snow case used forcing for water year 2003.

Methodology and Data

• Models used: ParFlow (v3.13), Common Land Model (CoLM, updated version 2024), old Common Land Model (CLM). The models were coupled through the top 10 soil layers, with ParFlow simulating 3D variably saturated subsurface flow and overland flow, and CoLM capturing water and energy processes from the canopy top to the root zone.
• Data sources: ERA5-Land reanalysis data (for meteorological forcing and evaluation of sensible heat, latent heat, skin temperature, and transpiration), Global Soil Dataset for Earth System Modeling (GSDE) for soil properties, GLHYMPS 1.0 for deep aquifer properties, and Snow Telemetry (SNOTEL) network observations for snow water equivalent (SWE) evaluation in synthetic cases.

Main Results

• Two decades of ParFlow-based coupled modeling have established the critical role of groundwater in modulating subsurface–land–atmosphere feedbacks, identified a critical water table depth (WTD) range (typically 0.5 m to 10 m) governing these interactions, and elucidated impacts of land cover and climate change on groundwater.
• The preliminary recoupling of ParFlow with the latest CoLM (CoLM/PF) demonstrates improved model performance compared to the old CLM/ParFlow (CLM/PF) when evaluated against ERA5-Land reanalysis and SNOTEL observations.
• CoLM/PF produces a more realistic partitioning of turbulent fluxes (increased latent heat, reduced sensible heat), substantially higher transpiration, and more accurately reproduces land surface temperature fluctuations.
• CoLM/PF generates a higher peak Snow Water Equivalent (SWE) that shows better agreement with SNOTEL observations in synthetic cases.
• CoLM/PF simulations exhibit greater variability in net water fluxes between the land surface and subsurface, leading to a generally deeper water table and a reduction in low levels of overland flow.
• A sustainable recoupling framework is proposed, advocating for a coupler-based architecture (e.g., ESMF/NUOPC), robust early-stage grid/process mapping, clear developer protocols for scalable upgrades, and a dedicated community interaction platform.
• A ParFlow-Land Surface Coupled Model Intercomparison Project (PLCMIP) is proposed to systematically evaluate coupled models, quantify groundwater–land–atmosphere interactions, assess parameter sensitivity, compare computational efficiency, and identify unique model strengths.

Contributions

• Provides a comprehensive synthesis of two decades of scientific advancements enabled by ParFlow-based coupled modeling systems, highlighting the critical role of groundwater in Earth system processes.
• Demonstrates the successful preliminary recoupling of ParFlow with the latest CoLM, showcasing improved performance and establishing a foundation for future, more comprehensive integrations.
• Proposes a novel, sustainable, and community-oriented framework for future ParFlow-LSM coupling, emphasizing modularity, interoperability, and long-term maintainability.
• Initiates the concept of a ParFlow-Land Surface Coupled Model Intercomparison Project (PLCMIP) to foster collaboration, standardize benchmarking, and guide the development of coupled models across the community.

Funding

• National Natural Science Fund for Excellent Young Scientists (Overseas) (grant no. 24EAA00330)
• Fundamental Research Funds for the Central Universities – Young Faculty Development Program (grant no. 25hytd008)
• National High-Level Young Talent Program (Provincial Government Matching Research Funds) (grant no. 2025HYSPT0705)
• Guangdong Major Project of Basic and Applied Basic Research (grant no. 2021B0301030007)

Citation

@article{Yang202620,
  author = {Yang, Chao and Sun, A and Zhang, Shupeng and DAI, YONGJIU and Kollet, Stefan and Maxwell, R. M.},
  title = {20 years of trials and insights: bridging legacy and next generation in ParFlow and Land Surface Model Coupling},
  journal = {Geoscientific model development},
  year = {2026},
  doi = {10.5194/gmd-19-1849-2026},
  url = {https://doi.org/10.5194/gmd-19-1849-2026}
}