Dense Media Radiative Transfer Applied to SnowScat and SnowSAR

Abstract

The dense media radiative transfer (DMRT) theory is applied to data analysis of recent measurements of multifrequency microwave backscatter from the snow cover on earth. Measurement includes ground-based campaign (SnowScat) and airborne mission (SnowSAR). Both the quasi-crystalline approximation (QCA) model and the bicontinuous model are used for a multilayer snow medium. Two size parameters are used for both models. Grain size and stickiness parameter are used for QCA model. The bicontinuous model has two parameters: the mean wave number ζ and the parameter b. The mean wave number ζ corresponds to the inverse of the grain size, while the b parameter controls the width of the wave number distribution and is related to the clustering property. The bicontinuous model is used to generate the microstructures of snow by computer, and Maxwell equations are solved numerically for each sample of computer-generated structure to calculate the extinction coefficient and the phase matrix. Other geometric descriptors of the bicontinuous medium include correlation functions and specific surface areas, both of which can be calculated from the parameters ζ and b. In making comparisons, we use ground measurements of specific surface area, grain size, densities, and layering of snow cover as input for the theoretical models. The geometric properties and the scattering properties of the bicontinuous model are also compared with past models. In making the multifrequency comparisons, we use the same physical parameters of all three frequencies: 1) X band; 2) Ku bands of 13.3 GHz; and 3) 16.7 GHz. It is emphasized that the DMRT models provide frequency, size, and angular dependence that depart from the classical model of Rayleigh scattering and are in better agreement with experimental observations. Index Terms-Bicontinuous, dense media radiative transfer (DMRT), quasi-crystalline approximation (QCA), remote sensing of snow, SnowSAR, SnowScat.

Estimating Snow Water Equivalent with Backscattering at X and Ku Band Based on Absorption Loss

“…The grain size distribution parameter b is an indicator of grain size distribution. As b decreases, the clustering effect becomes stronger and aggregation effects are stronger [32].…”

Nordic Snow Radar Experiment

“…Chang et al (2015) applied the SnowScat observations for comparisons of backscattering estimates using two derivations of the dense media radiative transfer (DMRT), the bicontinuous model and quasi-crystalline approximations (QCAs). The bicontinuous approach is based on exact solutions of the Maxwell equations, while QCA is an analytical approximation.…”

“…Data collected during NoSREx have found use in numerous recent studies exploring the modelling of microwave signatures of snow-covered terrain (Proksch et al, 2015b;Tan et al, 2015;Chang et al, 2015;Pan et al, 2016). Here, we provide an overview of the instrumentation and data acquisition protocols used and of the collected microwave signatures.…”

MEMLS3&a: Microwave Emission Model of Layered Snowpacks adapted to include backscattering

“…Together with complete 3-D microstructural information, these types of idealized experiments will allow us to minimize spatial variability, avoid the influence of the ground and compare different microstructural concepts for scattering coefficients. Together with available multi-layer models like MEMLS3&a, DMRT-ML or the DMRT-QMS package (Chang et al, 2014), this will clarify our understanding of the processes involved in microwave emission and scattering of snow.…”

“…However, scatterers are densely packed in snow and strongly interact with each other. More realistic models based on dense media radiative transfer (DMRT) have been developed (Tsang et al, 2007;Chang et al, 2014), including the possibility of using the numerical solution of Maxwell's equations for the single-layer scattering coefficients (Ding et al, 2010;Xu et al, 2012). The DMRT-based models however require at least two microstructural input parameters, which can be presently obtained only by µCT and often require time consuming casting procedures in the field.…”