On the Relationship Between Stickiness in DMRT Theory and Physical Parameters of Snowpack: Theoretical Formulation and Experimental Validation With SNOWPACK Snow Model and X-Band SAR Data

This study aims at relating the stickiness parameter ( $\tau$ ) of the dense media radiative transfer theory in quasi-crystalline approximation of Mie scattering of densely packed sticky spheres (DMRT-QMS), to the physical parameters of the layered snowpack. A relationship has been derived to express $\tau $ , which modulates the attractive contact force between ice spheres, as a function of ice volume fraction ( $\phi $ ) and coordination number ( $n_{c}$ ). Since $\tau $ is not a measurable parameter, this is a step forward with respect to what is commonly made in the literature, where $\tau $ is assumed as an arbitrary parameter, generally ranging between 0.1 and 0.3, to fit simulated backscattering data with those measured. As a first validation, DMRT-QMS was integrated with the SNOWPACK model to simulate backscattering at X-band (9.6 GHz) driven by nivo-meteorological data acquired on a test area located in Monti Alti di Ornella, Italy. The simulations were compared with Synthetic Aperture Radar COSMO-SkyMed (CSK) satellite observations. The results show a significant agreement ( $R^{2} =0.68$ ), although for a limited dataset of eight points in a unique winter season.