Snow Falling in Action

A hovering drone is circling a novel field deployable imaging system in action in the Davoser Alps during nighttime operation. This new imaging system is purposefully designed to track large amounts of snowfall in three dimensions. The system encompasses sixteen high-resolution cameras that are distributed over seven ice-fishing tents in a semi-circular configuration. The cameras stream their vast data from the blue tents to eight measurement computers situated in the red tents, while from the orange tent, a single laptop and pulse generator trigger the system in synchrony. The snow is continuously illuminated by multiple powerful stadium illumination panels that are retrofitted with custom-made cylindrical lenses and are configured in a line formation. The total field infrastructure entails over half a tonne of equipment and hundreds of meters of field cabling and is powered by high-capacity battery packs. The motion picture displays millions of snowflakes falling together in real time; the drone path further reveals the three-dimensionality of the large objective measurement volume over tens of meters. The lens flare on top of the image underscores the brightness of the illumination system, revealing a reflection of the individual LED modules. Illuminating millions of snowflakes falling together in the alpine night skies will shed new light on the intricate snow-clustering dynamics present in the atmospheric surface layer.

This work is performed in the group of Prof. Filippo Coletti at the Institute of Fluid Dynamics (ETH Zurich) and under the support of Prof. Michael Lehning at the Institute for Snow and Avalanche Research (WSL-SLF). Special credit goes out to Rafael Bölsterli (drone pilot) and support during deployment by Pim Bullee, and Yifan Wang.