MODELING SYNTHETIC-APERTURE RADAR (SAR) SCATTERING FROM A SEASONALLY VARYING SNOW-COVERED SEA-ICE VOLUME AT 5.3 AND 9.25 GHZ

A series of sensitivity analyses using dielectric, mixture and microwave scattering models is presented. Data from the Seasonal Sea Ice Monitoring and Modeling Site (SIMMS) in 1990 and 1991 are used to initialize the models. The objective of the research is to investigate the role of various geophysical and electrical properties in specifying the total relative scattering cross section (sigma0) of snow covered first-year sea ice during the spring period. The seasonal transition period from the Winter SAR scattering season to Early Melt was shown to signal a transition in dielectric properties which caused the snow volume to become a factor in the microwave scattering process. The effect of the thermal insulation of a snow cover on sea ice was shown to be significant for both epsilon' and epsilon''. Higher atmospheric temperatures caused proportionally greater changes in the dielectric properties of the sea ice at the base of the snow cover. Model sigma0 was computed for a range of sensor, sensor-earth geometry, and geophysical properties. In the Winter season the surface roughness terms (sigma(h) and L) were shown to have a significant impact on sigma(0) when the ice surface was the primary scattering mechanism. Once the snow cover began to warm and water was available in a liquid phase, the ice surface became masked because of the decrease in microwave penetration depths. During this period the water volume variable dominated sigma(0), both from its impact on sigma(v)0, and due to its control over the dielectric mismatch created at the air/snow interface.