Terrestrial Radar Observations of Dynamic Changes in Alpine Snow

Remote sensing of snow with active and passive microwaves on terrestrial, aerial, and satellite platforms has a long tradition. However, the observation of dynamic processes on alpine slopes is difficult due to fixed satellite orbits and consequently given observation geometry and interval and in some cases, also the lack of spatial resolution. Furthermore, the interferometric phase can only be used for displacement measurements if the displacement direction is more or less in the line of sight direction and the observation interval is shorter than the decorrelation time. The use of a terrestrial radar interferometer allows to overcome some of these constraints thanks to the portability of the system, the possibility to make repeat acquisitions in short intervals, and the regional observation capability. In this study, the GPRI (GAMMA portable radar interferometer, [1]) was used that is easily deployable in the field, produces images at meter scale resolution, and allows repeat acquisitions within a minute. Results of two campaigns conducted in the Swiss Alps prove the potential of terrestrial radar to measure rapid and local changes in snow parameters such as changes in the liquid water content and sudden changes in the snowpack due to skiers and avalanches. Using standard interferometric techniques, it was also possible to compute a regional snow displacement map providing information about creeping snow locations, displacement rates, and history.