An overview of passive microwave snow research and results

Abstract

The current state of knowledge of the microwave properties of snow is discussed. Theory behind the microwave emission from snow is reviewed, as are the physical processes of snowpack metamorphism. Field, aircraft, and satellite passive microwave data have been acquired and analyzed for more than 10 years. Results have repeatedly demonstrated the feasibility of employing multifrequency passive microwave data to study snow‐covered area, snow depth, and internal snowpack properties. Radiation emanating from the ground beneath a snowpack is scattered by the snow crystals, and concurrently, the snow itself emits radiation at microwave frequencies. Thus the radiation emerging from the snowpack is the result of a complex series of interactions both within and beneath the snowpack. Future studies recommended by a snowpack properties working group consisting of government and university scientists are discussed in detail. Recommendations include performing extensive laboratory measurements using real and artificial snow, to be coordinated with theoretical modeling and aircraft overflights carrying passive microwave instrumentation. This is considered necessary in order to help to interpret the microwave responses to snow.