Modeling the Thermal Infrared Emissivity of Snow and Ice Using Photon Tracking

• Published in: IEEE transactions on geoscience and remote sensing Vol. 62; pp. 1 - 8
• Main Authors: Xiong, Chuan, Yuan, Liang, Wang, Zhenzhan, Shi, Jiancheng
• Format: Journal Article
• Language: English
• Published: New York IEEE 2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Approximation; Climate; Climate models; Climate prediction; Density; Emissivity; Geometrical optics; Grain size; Ice; Infrared tracking; Mathematical models; Microstructure; Modelling; Optics; Particle size; photon tracking; Photonics; Photons; Radiation measurement; Remote sensing; Scattering; Sensitivity; Snow; Snow density; Spectral sensitivity; thermal infrared (TIR) emissivity; Thermal radiation
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2024.3454791

The thermal infrared (TIR) emissivity and physical temperature of snow together determine the thermal radiation of snow. The modeling of snow and ice TIR emissivity is important for climate models and remote sensing. Previous snow and ice TIR emissivity models fail in predicting the sensitivity of emissivity to snow type and snow microstructure, which was measured in experiments. Empirical models were proposed to simulate such sensitivity but not in a unified theoretical framework. In this study, we propose a snow and ice TIR emissivity model based on photon tracking by assuming that the geometric optics approximation is still valid in TIR spectral region. It is proved that the proposed model can predict both the TIR emissivity's sensitivity to grain size for small grain sizes and the TIR emissivity's sensitivity to snow density. These features can fully explain the experiment observed features. Moreover, the proposed model simulates snow and ice TIR emissivity in a unified theoretical framework. We also explain that the observed emissivity's sensitivity to snow type is actually caused by the sensitivity to snow density, not grain size. This proposed model can be further used in climate models and remote sensing.