Microwave Emission Model for Wet Snow by Using Radiative Transfer and Strong Fluctuation Theory

Abstract

Abstract-This study is concerned with the development of a model to describe microwave emission from terrain covered by wet snow. The model is based on the radiative transfer theory and the strong fluctuation theory. Wet snow is treated in the model as a mixture of dry snow and water inclusions. The shape of the water inclusions is taken into account. The effective permittivity is calculated by using the two-phase strong fluctuation theory model with nonsymmetrical inclusions. The phase matrix and the extinction coefficient of wet snow for an anisotropic correlation function with azimuth symmetric are used. The vector radiative transfer equation for a layer of a random medium was solved by using Gaussian quadrature and eigen analysis. The model behaviour is illustrated by using typical parameters encountered in microwave remote sensing of wet snow. Comparisons with emissivity data at 11, 21 and 35 GHz are made. It is shown that the model predictions fit the experimental data.

Comparison of the multi-layer HUT snow emission model with observations of wet snowpacks

“…When the HUT model is used for wet snow, it is necessary to consider how to define the absorption coefficient and the scattering coefficient of wet snow. Like the absorption coefficient of dry snow, the absorption coefficient of wet snow can also be calculated as a function of snow permittivity (Hallikainen et al ., ; Wang et al ., ) as: where k 0 is the wave number in free space, ε ws is the snow permittivity.…”

“…Two representative semi‐empirical models are the Helsinki University of Technology (HUT) model (Pulliainen et al ., ) and the Microwave Emission Model of Layered Snowpacks (Wiesmann and Matzler, ), and two widely used theoretical models are the Dense Media Radiative Transfer (DMRT) model (Tsang et al ., ) and the Strong Fluctuation Theory (SFT) model (Stogryn, ). Of all these models, more studies are carried out to revise a dry snow emission model to a wet snow emission model based on the SFT (Wang et al ., ; Arslan et al ., ) and the DMRT theory (Li, ; Tedesco et al ., ). In the SFT model, the wet snow is treated as a mixture of dry snow and water inclusions, and the azimuthally symmetric correlation function and the effective permittivity of wet snow are recalculated (Arslan et al ., ; Wang et al ., ).…”

“…Of all these models, more studies are carried out to revise a dry snow emission model to a wet snow emission model based on the SFT (Wang et al ., ; Arslan et al ., ) and the DMRT theory (Li, ; Tedesco et al ., ). In the SFT model, the wet snow is treated as a mixture of dry snow and water inclusions, and the azimuthally symmetric correlation function and the effective permittivity of wet snow are recalculated (Arslan et al ., ; Wang et al ., ). In the DMRT model, the wet snow is modeled as a mixture of ice particles surrounded by a thin film of water embedded in an air background.…”