A novel laser-based instrument for depth-resolved snow density estimation

• Main Authors: Koßagk, M., Neubert, M., Adams, M., Fromm, R., Silderhuis, H., Krause, R., Schaufelberger, G., Schmiel, T.
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Arctic
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5021478

Snow density is a key parameter for characterising snowpack stratigraphy. Estimating depth-resolved snow density and its spatial distribution are essential to calculate loads over weak layers or determine the snow water equivalent of a snowpack. However, direct manual snow density observations are typically time-consuming and potentially incomplete, while spaceborne and airborne methods are still in development. In this presentation, we introduce a new laser-based instrument for estimating snow density. The Snow Laser Drill (SLD) integrates a high-energy laser (1.5 µm, 3.4 – 15.4 W) with a laser rangefinder (0.6 nm), which are collinearly combined at a dichromatic mirror and directed towards the snow surface at a right angle. While the fist laser continuously drills into the snowpack, the second concurrently measures hole depth and thus penetration speed. Based on the correlation of penetration rate with snow density and temperature, a depth-resolved density profile of the entire snowpack can be derived in the millimetre-range. The system was developed and calibrated in a series of lab experiments, which resulted in two prototype SLDs. These were trialled in several field tests in the Alps and the Arctic in the winters 2021/22 and 2022/23. During these campaigns, different laser output power, beam diameter and divergence angles were tested. SLD data were compared with manual snow density observations and by-proxy snow density calculations derived from SnowMicroPen measurements. We present first results from lab and field tests and discuss the potential and limitations of the new instrument as well as an outlook on future applications.