Collection: Ice load and fog sensor

Snow is frozen, usually flat, crystallized precipitation. Its density and weight depend primarily on the air temperature at the time of snowfall—throughout the entire atmosphere—and also during the snow's duration. This influences the crystallization and agglomeration pattern. Snow usually forms a hexagonal-star-shaped crystal structure, which can interlock to form large snowflakes even during snow formation. Once in the snow, the snow changes into a highly complex structure due to the addition of additional layers and recrystallization.
Fresh snow has a specific gravity of 0.03 (dry, freshly fallen snow) to 0.2 (well-set new snow without additional water absorption). In terms of pressure, one meter of powder snow corresponds to a water column about five to ten centimeters high; for paper snow (wet snow) it is about 20 cm, or 50–200 liters per square meter of precipitation (water equivalent). One cubic meter of water weighs one ton (1000 kg), so one cubic meter of fresh snow weighs 30–200 kg, and snow that has been lying for longer often weighs much more. Snow load generally acts as a distributed load perpendicular to the surface. For static analysis, the load assumption is simplified – and to be on the safe side – based on wet snow and a specific gravity (specific gravity, weight per volume) of 2 kN/m³. This roughly corresponds to the value mentioned above for tightly bound new snow.
Snow pressure is a general term used in relation to landscape (e.g. forestry or ecological), but in construction terms it would specifically mean the weight force or, more precisely, the force per contact surface, i.e. the actual surface pressure.
When it settles, the snow cover does not become heavier, it only reduces its volume. In fact, snow essentially becomes lighter as it lies, both in warm weather and in extreme cold after snowfall: In the first case, the snow melts, seeps through the pores and runs off; in the second case, the water sublimates ("evaporates") directly into the air. This is favored by sunshine and dry air. From a structural point of view, even several meters of dry, fresh snow on technically sound roofs pose no threat. Heavy snowfalls at temperatures around or above zero degrees Celsius are problematic, because very heavy snow falls in these cases, and even more so when rainfall falls into deep snow covers. Large quantities of additional water can then be bound in the snow cover, and the snow load actually increases many times over, which can lead to spontaneous roof failure. This can happen within a few hours. Therefore, prolonged snowfalls and heavy snow turning into rain represent acute crisis scenarios. Fog frost, the term for the deposited precipitation of rime, hoarfrost, and clear ice, is formed by supercooled fog droplets that spontaneously freeze on obstacles whose surface temperatures are also below 0ºC. The resulting deposits can reach considerable weight, especially in high altitudes in low mountain ranges, endangering forests, power lines, and pylons, especially since such weather conditions are often accompanied by high wind speeds.