Abstract
Providing ground truth for the backscatter and absorption effects of a snow cover on electromagnetic waves has long been a problem. One characteristic of the snow cover which has been particularly difficult to measure is its free, or liquid, water content - the fraction of the snow's volume which exists in the liquid state. Five methods which have been used for measuring this parameter are described and their merits and deficiencies discussed. Two of the methods are calorimetric, measuring the free water content as a function of the heat added to or removed from a snow sample while completely melting or freezing it. The third uses the freezing point depression observed on adding a salt solution to a snow sample to calculate the snow's free water content. In the fourth procedure, a snow sample is completely dissolved in ethyl or methyl alcohol. The corresponding decrease in temperature is inversely related to the free water content of the snow. The final technique is electronic: above a certain frequency, the electrical capacitance of snow is related to its density and free water content. With accurate calibration, devices which measure snow capacitance are likely to be the simplest and fastest means of providing free water measurements.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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