Methodology:

The rain-on-snow percolation experiment used a coloured water tracer of known temperature (12.4 degrees C) and volume (2000mL), which is applied over a defined area (40 cm x 20 cm). Tracer advance within the snowpack is visible based on its blue colour. The duration of tracer application, which can be used to calculate melt flux, was 68 seconds. The evolution of temperature was monitored with five thermometers placed in regular intervals (63cm, 60cm, 55cm, 45cm snow height) at 30-second resolution over a period of 19 minutes. The experiment was concluded when the start of refreezing was evident as decreasing temperature of the top thermometer. When the start of refreezing was evident from the decreasing temperature in the top thermometer.

The video material has been cropped to focus on the spatial extent of the snow pit front and the duration of the experiment. The yellow foldable ruler provides the scale. The timelapse video (1:11 min) captures the full 19-minute experiment duration. The original video has been sped up 16-fold to create the timelapse.

Data collection:

Dimensions of snow pit front: horizontal width = 40 cm, average snow depth = 65.5 cm

The video was recorded with the camera of a SAMSUNG Galaxy A52s mobile phone while positioned in the snow pit using a tripod. The video was processed using the Android Samsung Gallery App.

Data quality:

Video quality: 720 pixels x 992 pixels (frame width x frame height)

Thermometers were placed at the following regular intervals: 63cm, 60cm, 55cm, 45cm snow height, equalling 2.5cm, 5.5cm, 10.5cm, 15.5cm, 20.5cm below the snow surface).