"Numerical modeling of microwave interactions with sea ice"

Abstract

Remote sensing is a key instrument for monitoring sea ice surface properties over large areas. Synthetic Aperture Radar (SAR) as well as Real Aperture Radar (RAR) are two types of radars that are extensively used in this context and measure the backscatter of the surface that they illuminate. Backscattering of waves from rough surfaces is complicated and depends, among other things, on the roughness of the illuminated surface and the surfaces material properties.

This thesis focuses on modeling the backscattering cross section from sea ice layers with rough surfaces on top of sea water, by designing a model that builds on the physical basis of electromagnetic wave theory and combines it with the Finite Element Method (FEM) approach. The model is designed as general as possible and can be adapted to various sea ice scenarios by modifying the chosen surface and material properties. Temperature, Density and Salinity (TDS) fieldwork measurements from Van Keulenfjord on Svalbard have been used to estimate realistic continuous permittivity profiles of sea ice using the Polder-van-Santen/de Loor mixture model and have been incorporated into the model.

The model has been validated by comparing its results for a perfectly flat surface to the Fresnel equations and a perfect agreement was achieved. It was also successfully validated using the Bragg scattering phenomena for periodic surfaces. Furthermore, a comparison between the results of the model and the Small Pertubation Model (SPM) was done for a slightly rough surface at different frequencies and permittivities, and clear similarities were observed.

Based on the confidence from the validations, the backscatter cross section of a sea ice/sea water scenario with continuous permittivity profiles has then been modeled.