Improvement in Modeling Soil Dielectric Properties During Freeze-Thaw Transitions

Abstract

Soil freeze-thaw cycles have a profound impact on heat and water fluxes at the land-atmosphere interface and transport in soils. Microwave remote sensing is a widely used technique to detect near-surface soil freeze/thaw states due to significant changes in dielectric properties associated with water phase transitions in soils, where uncertainty remains. This letter proposed a new parameterization scheme for the estimation of unfrozen water content to improve the modeling of soil dielectric properties during freeze-thaw transitions. Predictions from the new model referred as Zhang-Zhao's model were compared with dielectric measurements during thawing processes of soil samples collected from Baoding (silty clay soil), Zhangjiakou (loamy sandy soil), and Zhengzhou (clay loam soil) in China. The mean biases of the predictions were 3.25 (4.44 and 2.07 for the thawed value and frozen value, respectively) and 1.54 (2.22 and 0.88 for the thawed value and frozen value, respectively) for the real part and imaginary part, respectively. The model-predicted soil complex relative permittivity was highly correlated with measurements, with correlation coefficients ranging from 0.7944 to 0.9865. The normalized root mean square errors of the predictions were 13.72% (real part) and 25.41% (imaginary part).

All-Season Liquid Soil Moisture Retrieval From SMAP

“…The 𝛼 is the shape factor constant. We made further modifications to the parameters (soil temperatures≧0 ℃, α = 0.85, soil temperatures < 0 ℃, α = 0.56) using global soil texture data based on Wu [28]. 𝑚 𝑣𝑢 is the unfrozen water expressed as follows [27].…”

“…Zhao et al [27] introduced a novel parametric approach to establish the correlation between unfrozen water, soil temperature, and initial SM. Wu et al [28] validated the new scheme using dielectric measurements from six types of soil samples. This model is now referred to as the Zhang-Zhao model.…”

A Soil Moisture Retrieval Method for Reducing Topographic Effect: A Case Study on the Qinghai–Tibetan Plateau With SMOS Data

“…It should be noted that this study assumes that the MTMA method will deliver a "very dry bare soil" (low dielectric constants) output when the soil temperature is lower than 273.13 K. The soils are considered as frozen soils when the soil temperature is less than 273.15 K. Although volume scattering may exist with increasing penetration depth for frozen soils [48,49], we assumed that it has only surface scattering as a very dry soil (low dielectric constants). Therefore, the liquid (unfrozen) soil moisture can be retrieved by using the Mironov's model (as used in this study) or other similar dielectric model suitable for frozen soils [50,51].…”

LAGRS-Soil: A Full-Polarization GNSS-Reflectometry Model for Bare Soil Applications in FY-3E GNOS-R Payload

“…Among these factors, temperature variations play a significant role in the transformation of soil freeze-thaw (F/T) processes. To calculate frozen soil DDMs, the Zhang-Zhao dielectric constant model is included in the LAGRS-Soil model to combine with the random roughness surface model [37,38].…”