Umair et al. (2026) Implementing a Plant Hydraulics Parameterization in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) v.1.4

Identification

• Journal: Journal of Advances in Modeling Earth Systems
• Year: 2026
• Date: 2026-01-01
• Authors: Muhammad Umair, Joe R. Melton, Alexandre Roy, Eller, Cleiton Breder, 1986-, Jennifer L. Baltzer, Bram Hadiwijaya, Bo Qu, Nia Perron, Oliver Sonnentag
• DOI: 10.1029/2024ms004385

Research Groups

• Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN-IPSL): Sorbonne Université/CNRS/IRD/MNHN, Paris, France.
• Centre National de Recherches Météorologiques (CNRM): Université de Toulouse, Météo-France, CNRS, Toulouse, France.
• Institute of Environmental Geosciences (IGE): Université Grenoble Alpes/CNRS/IRD/Grenoble INP, Grenoble, France.
• European Centre for Medium-Range Weather Forecasts (ECMWF): Reading, UK.

Short Summary

This study evaluates the impact of assimilating satellite-derived Leaf Area Index (LAI) and Surface Soil Moisture (SSM) into the ISBA-CTRIP land surface model over the Euro-Mediterranean region. The results demonstrate that joint assimilation significantly improves the representation of vegetation dynamics and river discharge, particularly in water-limited areas.

Objective

• To assess the performance of the LDAS-Monde (Land Data Assimilation System) in co-assimilating satellite-derived Surface Soil Moisture (SSM) and Leaf Area Index (LAI).
• To evaluate the impact of this assimilation on the simulation of terrestrial water storage (TWS), river discharge, and vegetation biomass over the Euro-Mediterranean domain.

Study Configuration

• Spatial Scale: Euro-Mediterranean region (25°N–75°N, 11.75°W–62.5°E) at 0.5° x 0.5° resolution.
• Temporal Scale: 2000–2012 (13 years), with a focus on seasonal and interannual variability.

Methodology and Data

• Models used:
  • ISBA-A-gs: Land surface model describing water and energy exchanges and vegetation growth.
  • CTRIP: River routing model coupled with ISBA to simulate streamflow and groundwater.
  • LDAS-Monde: Integration platform using a Simplified Extended Kalman Filter (SEKF).
• Data sources:
  • Forcing: ERA-Interim reanalysis.
  • Assimilation: Copernicus Global Land Service (CGLS) LAI and ESA CCI combined SSM.
  • Validation: GRACE (TWS), Global Runoff Data Centre (river discharge), and independent satellite vegetation products.

Main Results

• Vegetation: Assimilation of LAI significantly reduced model biases, particularly in the Mediterranean, increasing the correlation with independent observations from 0.75 to 0.90.
• Soil Moisture: SSM assimilation improved the simulation of root-zone soil moisture, which in turn enhanced the coupling between water availability and plant growth.
• Hydrology: River discharge simulations showed improved Nash-Sutcliffe Efficiency (NSE) in 65% of the stations, with notable gains in the Ebro and Po basins.
• Terrestrial Water Storage: The LDAS-Monde showed a high correlation (0.85) with GRACE satellite data, effectively capturing the interannual depletion of water storage during drought years (e.g., 2003, 2011).

Contributions

• Demonstrates the feasibility and added value of a multi-variable (SSM + LAI) assimilation approach at a continental scale.
• Provides a robust framework for monitoring land surface states (droughts, floods, biomass production) by bridging the gap between satellite observations and physical modeling.
• Highlights the critical role of vegetation dynamics in regulating the hydrological cycle in semi-arid regions.

Funding

• European Union’s Horizon 2020: ImagineS project (grant agreement No. 311766).
• Météo-France and CNRS: Institutional support.
• EUMETSAT: Support via the H-SAF (Hydrology Safe) project.

## Citation
```bibtex
@article{Umair2026Implementing,
  author = {Umair, Muhammad and Melton, Joe R. and Roy, Alexandre and Eller, Cleiton Breder, 1986- and Baltzer, Jennifer L. and Hadiwijaya, Bram and Qu, Bo and Perron, Nia and Sonnentag, Oliver},
  title = {Implementing a Plant Hydraulics Parameterization in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) v.1.4},
  journal = {Journal of Advances in Modeling Earth Systems},
  year = {2026},
  doi = {10.1029/2024ms004385},
  url = {https://doi.org/10.1029/2024ms004385}
}

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