Wang et al. (2026) Modeling saline soil complex permittivity from bound-water microphysics: Laboratory validation at L-/C-bands

Identification

• Journal: Remote Sensing of Environment
• Year: 2026
• Date: 2026-04-04
• Authors: Jundong Wang, Zhigang Sun, Wanxue Zhu, Lidong Ren, Ehsan Eyshi Rezaei
• DOI: 10.1016/j.rse.2026.115386

Research Groups

• Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (CAS)
• CAS Engineering Laboratory for Yellow River Delta Modern Agriculture, Institute of Geographic Sciences and Natural Resources Research, CAS
• University of Chinese Academy of Sciences
• Shandong Dongying Institute of Geographic Sciences
• National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences
• Leibniz Centre for Agricultural Landscape Research (ZALF)

Short Summary

This study develops a microphysical-electromagnetic coupling model for soil complex permittivity (SCP) in saline soils, validated in the laboratory across L- and C-bands. The proposed model achieves high accuracy (R² > 0.95) and outperforms existing models, demonstrating its potential for improving microwave remote sensing of soil salinity.

Objective

• To develop a generalizable, high-precision microphysical-electromagnetic coupling soil complex permittivity (SCP) model framework for saline soils over 1–6 GHz (L-band and C-band) to improve microwave remote sensing of soil salinity.

Study Configuration

• Spatial Scale: Laboratory-scale measurements on six diverse types of soil samples.
• Temporal Scale: The model is optimized and validated for microwave frequencies from 1 GHz to 6 GHz.

Methodology and Data

• Models used: Dynamic Cole-Cole model, Poisson-Bikerman model, soil volumetric four-component scheme. These are integrated into the proposed microphysical-electromagnetic coupling SCP model.
• Data sources: Laboratory measurements of Soil Complex Permittivity (SCP) using the coaxial probe method on prepared soil samples (desalination-drying preparation, gradients of soil salinity and soil moisture). Scenario-based Synthetic Aperture Radar (SAR) simulations and evaluation against Sentinel-1 observations for C-band SAR backscattering coefficients.

Main Results

• The proposed SCP model achieved R² = 0.955 and Normalized Root Mean Square Error (NRMSEσ) = 0.213 for the real part (εʹ soil), and R² = 0.960 and NRMSEσ = 0.200 for the imaginary part (ε˝soil) on an independent testing set.
• Per-sample median R² values for εʹ soil and ε˝soil were generally around 0.95 upon generalization to 1–6 GHz.
• Salinity predominantly affects the imaginary part (ε˝soil) of SCP.
• L-band is more sensitive to salinity, whereas C-band is more stable.
• Once the soil solution approaches the solubility limit with salt precipitation, further increases in soil salinity have little discernible effect on SCP.
• The proposed SCP model outperforms existing saline-soil dielectric models on the laboratory dataset.
• Scenario-based SAR simulations indicate the model's added value is most evident for L-band satellite observations under low soil moisture, typical surface roughness, and saline conditions.
• SCP-driven forward simulations of C-band SAR backscattering coefficients, evaluated against Sentinel-1 observations, support the physical feasibility of the proposed SCP model for microwave remote-sensing applications.

Contributions

• Development of a novel microphysical-electromagnetic coupling SCP model framework that integrates a dynamic Cole-Cole model, a Poisson-Bikerman model, and electric-field suppression into a soil volumetric four-component scheme.
• Provides a generalizable, high-precision mechanistic basis for describing SCP over 1–6 GHz, addressing a gap in existing soil dielectric models.
• Outperforms existing saline-soil dielectric models in laboratory validation.
• Demonstrates potential for extension to higher-clay soils (approximately 40%) and varying ionic compositions and temperature regimes.
• Supports operational microwave remote sensing of soil salinity through improved SCP modeling, particularly for L-band SAR under specific conditions.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Wang2026Modeling,
  author = {Wang, Jundong and Sun, Zhigang and Zhu, Wanxue and Ren, Lidong and Rezaei, Ehsan Eyshi},
  title = {Modeling saline soil complex permittivity from bound-water microphysics: Laboratory validation at L-/C-bands},
  journal = {Remote Sensing of Environment},
  year = {2026},
  doi = {10.1016/j.rse.2026.115386},
  url = {https://doi.org/10.1016/j.rse.2026.115386}
}