Microwave characteristics of snow

A program is underway at NBS to measure the microwave scattering characteristics of snow. Microwave signals nondestructively penetrate snow, but they are modified by the material properties of snow (density, free moisure content, resistance, temperature). There is a distinct possibility of developing miniaturized microwave instrumentation to remotely sense and measure those undisturbed snow properties as a function of time and depth. A portable FM-CW system was developed to measure electromagnetic profiles of snow packs down to ground level. This system was used to monitor changes in snow stratigraphy as a function of time of day. An Automated Network Analyzer system was used to measure the elecromagnetic scattering properties of snow at discrete frequencies over the range 250 MHz - 18 GHz. the snow was physically analyzed in terms of resistance, temperature, and density profiles, and by visual characterization. Some experiments included measurement of global radiation and liquid water at the snow surface.