Helicopter-based Microwave Radar Measurements in Alpine Terrain

Due to the time-consuming nature of traditional snowpit measurements, and the large spatial variability that often exists in alpine snowpacks, tools which can rapidly characterize snowpack properties are in great need. Microwave radar has an additional advantage in that it is non-destructive and measurements can be made remotely, providing the opportunity to make measurements over large areas rapidly from an airborne platform. Signal interpretation can be difficult, however recently several ground-based studies have shown that the technique can be used to accurately measure snow depth, snow water equivalent, and snow stratigraphy. Accurate measurements of these properties from the air is much more challenging, especially in steep terrain. We present results from two field campaigns near Valdez, Alaska, in which measurements in mountainous terrain were made from a helicopter with two different FMCW radar systems. Snow depth and stratigraphy was visible at altitudes of less than 100 feet, while steep terrain made interpretation difficult at typical flying altitudes, due to the footprint size of the radar. Refinements of helicopter-based radar measurements may eventually provide a useful tool to assist in stability evaluations for helicopter ski operators.