SNOW PROBE FOR IN-SITU DETERMINATION OF WETNESS AND DENSITY

The amount of water present in liquid form in a snowpack exercises a s trong influence on the radar and radiometric responses of snow. Conven tional techniques for measuring the liquid water content m(v) suffer f rom various shortcomings, which include poor accuracy, long analysis t ime, poor spatial resolution, and/or cumbersome and inconvenient proce dures. This paper describes the development of a hand-held electromagn etic sensor for quick and easy determination of snow liquid mater cont ent and density. A novel design of this probe affords several importan t advantages over existing similar sensors. Among these are improved s patial resolution and accuracy, and reduced sensitivity to interferenc e by objects or media outside the sample volume of the sensor. The sen sor actually measures the complex dielectric constant of the snow medi um, and the mater content and density must be obtained through the use of empirical or semi-empirical relations. To test the suitability of existing models and allow the development of new models, the snow prob e was tested against the freezing calorimeter and gravimetric density determinations. From these comparisons, valid models were selected or developed. Based on the use of these models, the following specificati ons mere established for the snow probe: 1) liquid mater content measu rement accuracy = +/-0.66% in the wetness range from 0 to 10% by volum e and 2) wet snow density measurement accuracy = +/-0.05 g/cm(3) in th e density range from 0.1 to 0.6 g/cm(3).