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Global Sensitivity Analysis of Seasonally Frozen Soil Radiation Transfer (SFS_DMRT) Model for Monitoring Soil Freeze-Thaw
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DOI：10.1109/tgrs.2026.3716637.png)
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Abstract
En 中文
The soil freeze-thaw (F/T) cycle plays a critical role in understanding the water cycle, climate change, and land–atmosphere energy exchange. Although passive microwave remote sensing is widely used for large-scale F/T monitoring, the sensitivity of frozen soil microwave radiation to soil parameters remains insufficiently understood, limiting improvements in monitoring accuracy. To address this gap, this study employs the Sobol global sensitivity analysis (SA) method in combination with the seasonally frozen soil radiation transfer (SFS_DMRT) model to evaluate the sensitivity of brightness temperature (Tb) under different frequencies, incidence angles, polarizations, and their combinations to key soil parameters. The results reveal a frequency-dependent transition in the dominant mechanisms affecting Tb. Specifically, L-band Tb is sensitive to microwave emission from the bottom unfrozen layer, whereas C- and X-bands Tb are primarily sensitive to emission from the upper frozen layer. Ku-band Tb is influenced by both emission and volume scattering within the upper frozen layer, while Ka-band Tb is mainly affected by volume scattering. Beyond these frequency-dependent mechanisms, the analysis also reveals how specific microwave configurations can serve as indicators for different soil parameters. V-polarized Tb (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V}}$ </tex-math></inline-formula>) exhibits sensitivity to frozen layer temperature. The polarization difference (PD) at C-band (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V}}{\,}-$ </tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {H}}$ </tex-math></inline-formula>) is sensitive to frozen depth, especially within the top 30 cm. The PD at L-band and the incidence angles difference of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V}}$ </tex-math></inline-formula> between 55° and 40° (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V55^{\circ }}}{\,}-$ </tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V40^{\circ }}}$ </tex-math></inline-formula>) are sensitive to the effective dielectric constant of the frozen layer. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Tb}_{\mathbf {V}}$ </tex-math></inline-formula> ratio between C- and Ka-bands is sensitive to volume scattering effects. By systematically evaluating the sensitivity of microwave radiation to key soil parameters, the global SA identifies optimal passive microwave configurations for monitoring soil F/T in response to variations in soil temperature, frozen depth, dielectric properties, and volume scattering during F/T transitions, thereby providing valuable guidance for improving soil F/T monitoring algorithms and offering insights for the design of future satellite payloads.
Keywords:
Global sensitivity analysis (SA)
passive microwave remote sensing
SFS_DMRT
soil freeze-thaw (F/T)
volume scattering
Journal
IF:
8.6
Papers:
2.1W
Citations:
10.7W
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