Modelling Microwave Backscattering from Sea Ice for Synthetic-Aperture Radar Applications

• Main Author: Carlström, Anders
• Language: unknown
• Published: 1995
• Subjects: Astronomy; Astrophysics and Cosmology; Electrical Engineering; Electronic Engineering; Information Engineering; synthetic-aperture radar; microwave; surface roughness; sea ice; backscattering models; Arctic; Arctic Ocean; Sea ice
• Online Access: https://research.chalmers.se/en/publication/1308

The spaceborne synthetic-aperture radar (SAR) is considered one of the key instruments for monitoring the ice cover in polar oceans and regional seas. This thesis is concerned with applications of electromagnetic scattering theory and SAR system theory for modelling the response of different types of sea ice in SAR imagery. The modelling is an important tool for improving the interpretation of SAR images. The emphasis has been on the frequency (5.3 GHz), polarization (vertical), and incidence angles (20 ° -26 °) used by the SAR onboard the first European Remote Sensing Satellite (ERS-1), which has been in operation since 1991. A SAR image simulator has been developed, which is able to closely simulate the first and second order statistics of the SAR image over a natural distributed target. It has been used to evaluate sea ice classification algorithms when applied to SAR images with different spatial and radiometric resolution. A number of field experiments in the Arctic Ocean and the Baltic Sea have been carried out involving coincident radar backscattering and surface characterization measurements with the objective to improve our understanding of the scattering physics involved. Surface scattering is modelled using accurate measurements of small-scale surface roughness with a laser profiler, which are input to the integral equation model (IEM). Volume scattering from air inclusions in the ice is estimated by a Rayleigh scattering model, which neglects multiple-scattering and dense medium effects. A new scattering model is formulated for deformed sea ice which consists of randomly oriented ice blocks. It is shown that the mean backscattering is independent of the block size distribution provided that sizes and slopes are independent. The model includes scattering from both the upper and lower sides of the blocks and it is shown that a superimposed surface roughness is of little importance. The model has been compared with numerical scattering computations using the method of moments. Good agreement is ...