A comparison of Ground-Based LiDAR, contact spectroscopy, FMCW radar, and manual snow pit profiles of a mountain snowpack

Manual field measurement of seasonal snow properties is time-consuming and often subjective, leading to difficulties with repeatability and obtaining adequate spatial coverage. Remote sensing observations provide non-destructive sampling and large spatial extents, but signal interpretation is frequently complicated by high spatial variability. Use of remote sensing technology via ground-based deployment offers the potential to bridge manual and remote observations, and aid interpretation and repeatability of both. We examine co-located profiles of snow properties in a single snow pit using a variety of observation techniques. Ground-based LiDAR scans of the vertical pit face using a 1550 nm wavelength full-waveform scanning LiDAR system provides 2 to 5 mm horizontal and vertical resolution that allows for quantifiable characterization of reflectivity, absorption and grain size. A contact spectroscopy profile at 2 cm vertical intervals provides spectral signatures, from which optical-equivalent grain size and specific surface area are inferred. A portable FMCW radar system returns a profile of backscatter energy with 1 cm vertical resolution, detailing layering and a vertical SWE distribution. A conventional manual profile of stratigraphy, grain size and type, and hardness allows comparison of profiles from the different technologies to standard field observation practices. This comparison at the point scale supports interpretation of data obtained using these different techniques, and analysis of field and remotely-sensed measurements of seasonal snowpack properties at multiple scales in mountain environments.