Hingerl et al. (2025) Comparative analysis of land–atmosphere interactions across three contrasting ecosystems in the West Sudanian Savanna

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-09-10
• Authors: Luitpold Hingerl, Jan Bliefernicht, Samuel Guug, Souleymane Sy, Frank Neidl, Thomas Jagdhuber, Harald Kunstmann
• DOI: 10.1016/j.ejrh.2025.102751

Research Groups

• Institute of Geography, University of Augsburg, Augsburg, Germany
• WASCAL Competence Center, West African Science Service Center on Climate Change and Adapted Land Use, Ouagadougou, Burkina Faso
• Institute for Meteorology and Climate Research, Campus Alpin, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany
• Microwaves and Radar Institute, German Aerospace Center (DLR), Wessling, Germany

Short Summary

This study conducted a multi-year analysis of energy fluxes and land–atmosphere coupling using eddy covariance data from three contrasting ecosystems in the West Sudanian Savanna to assess land use change impacts. It found significant alterations in energy partitioning and land-atmosphere coupling, especially during dry and transitional seasons, driven by vegetation structure and soil moisture.

Objective

• How do different land use types at the three sites affect the radiative properties and the partitioning of energy fluxes under similar climatic conditions?
• What are the potential drivers of the spatiotemporal variability in land–atmosphere interactions?
• How do different land use types affect land–atmosphere coupling properties?

Study Configuration

• Spatial Scale: Three contrasting ecosystems (near-natural savanna, cropland, degraded grassland) in the West Sudanian Savanna (northern Ghana and southern Burkina Faso). Eddy covariance flux footprints extend up to 150 meters upwind.
• Temporal Scale: Multi-year analysis over a three-year period (2013–2015).

Methodology and Data

• Models used:
  • TK3 for eddy covariance data processing and quality control.
  • REddyProc package for R for gap-filling flux data.
  • NOAH land surface model (version 3.4.1) for gap-filling evapotranspiration (ET) time series.
  • R Bigleaf package for calculating surface parameters.
  • Backwards trajectory Lagrange model (Kljun et al., 2015) for flux footprint prediction.
• Data sources:
  • Eddy covariance (EC) measurements (sonic anemometer, infrared open path gas analyzer, net radiometer) from three sites.
  • Satellite-derived Leaf Area Index (LAI) from MOD15A2H version 6 data (500 m spatial resolution).
  • Meteorological data from nearby weather stations for gap-filling.

Main Results

• Significant disparities were observed in radiation variables (albedo up to 30%, net radiation up to 45%) and turbulent fluxes across contrasting land use sites, particularly on seasonal and diurnal scales.
• Evaporative fraction (EF) was markedly altered (up to 30% lower) at agricultural sites compared to the near-natural savanna during the dry season and both transitional phases of the West African Monsoon.
• Smaller differences in EF were observed between degraded grassland and cropland, primarily due to distinct physiological properties of the vegetation and differences in land management practices (grazing vs. crop cycles).
• Partial correlation analysis identified key drivers of land–atmosphere interactions:
  • The degraded grassland site exhibited the highest sensitivity of EF to LAI (Spearman correlation coefficient, r = 0.54).
  • Soil moisture in the upper layers exerted significant control on evapotranspiration at both altered sites (r = 0.53 for cropland, r = 0.56 for degraded grassland), but much lower control at the savanna site (r = 0.23), indicating relevant contribution of water uptake through deep roots.
• Land–atmosphere coupling was primarily altered during the drying phase of the West African Monsoon.
• Physiological differences, described by surface conductance, were significant between the near-natural savanna and the altered sites during the rainy season and the wet-to-dry transitional period, with values around three times higher at the near-natural savanna.
• Aerodynamic properties were distinct between the savanna site (aerodynamic conductance ranging from 95 to 120 mm/s) and the altered sites (30 to 50 mm/s) throughout the year.
• Calculated flux footprints, encompassing the areas from which 80% of the fluxes originate, extend up to 150 meters upwind, revealing consistent seasonal patterns and confirming data representativeness.

Contributions

• Presents, for the first time, a detailed, multi-year (3-year) analysis of energy fluxes and radiation components across three contrasting ecosystems (near-natural savanna, cropland, degraded grassland) in the West African Sudanian savanna, utilizing exceptionally high-quality and consistent eddy covariance data.
• Provides critical ground-based evidence on how land use influences land–atmosphere interactions in this understudied, data-scarce region.
• Offers insights essential for refining regional climate and hydrological models, and for informing climate adaptation, sustainable land management, and water resource planning in a region facing rapid environmental change.

Funding

• WASCAL (West African Science Service Center on Climate Change and Adapted Land Use), granted by the Federal Ministry of Education and Research in Germany (grant number: 01LG1202C1).
• Federal Ministry of Education and Research of Germany (BMBF) through the Concerted Regional Modeling and Observation Assessment for Greenhouse Gas Emissions and Mitigation Options under Climate and Land Use Change in West Africa (CONCERT-West Africa; grant number 01LG2089A BMBF).

Citation

@article{Hingerl2025Comparative,
  author = {Hingerl, Luitpold and Bliefernicht, Jan and Guug, Samuel and Sy, Souleymane and Neidl, Frank and Jagdhuber, Thomas and Kunstmann, Harald},
  title = {Comparative analysis of land–atmosphere interactions across three contrasting ecosystems in the West Sudanian Savanna},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102751},
  url = {https://doi.org/10.1016/j.ejrh.2025.102751}
}