Modeling Active Microwave Remote Sensing of Multilayer Dry Snow using Dense Media Radiative Transfer Theory

In this paper, we model the backscattering coefficients of multi-layer dry snowpacks, based on Dense Media Radiative Transfer theory (DMRT) with the Quasicrystalline Approximation (QCA). The DMRT model accounts for adhesive aggregate effects, which leads to dense media Mie scattering by using a Sticky particle model. The same set of DMRT equations are used for modeling both active and passive remote sensing. The model is validated by using the Cold-Land Processes Field Experiment CLPX ground based polarimetric scatterometry observation at local-scale observation site (LSOS) and airborne polarimetric Ku-band scatterometer (POLSCAT) data at Fool-Creek, Fraser. The snow density profiles are from ground observation and grain sizes are fitting parameters. It shows that the co-polarization simulations are in good agreement with the data, the cross-polarization simulations are around 2 dB lower than ground based observation and 5 dB lower than airborne observation. With the same set of multi-layer snowpack profile, the QCA/DMRT model matched co-polarization backscattering coefficients and all 4 channels of brightness temperature observations simultaneously at LSOS. The cross-polarization simulation can be improved by 3-dimensional numerical solutions of Maxwell equations (NMM3D). Study at Fool-Creek shows that NMM3D/DMRT simulations can match both co-polarization and cross-polarization observations simultaneously.