HIM - Electronic sensors for the determination of iload and fog frost

Snow is frozen precipitation, usually crystallised in sheets, whose density and weight depend primarily on the air temperature, at the time of snowfall - at the entire atmospheric height - thus also during the lying time: It influences the crystallisation and agglomeration form. Snow forms a normally hexagonal-star-shaped crystal form, which can interlock to form large snowflakes even during snow formation. When lying on the ground, the snow changes into a highly complex structure due to the accumulation of further layers as well as recrystallisation.
Fresh snow has a specific weight of 0.03 (dry freshly fallen snow) to 0.2 (well-set fresh snow without additional water absorption). In terms of pressure, one metre of powder snow corresponds to a column of water about five to ten centimetres high, in the case of cardboard snow (wet snow) it is about 20 cm, i.e. 50-200 litres per square metre of precipitation (water equivalent). A cubic metre of water weighs one tonne (1000 kg), a cubic metre of fresh snow thus 30-200 kg, longer lying snow often much more.Snow load generally acts as a surface load perpendicular to the base area. For static verifications, with regard to the load assumption, it is simplified - and on the safe side - to calculate with wet snow and a weight (specific weight, weight force per volume) of 2 kN/m³, which corresponds approximately to the above-mentioned value for strongly bound fresh snow.
Snow pressure as a general word is synonymous with landscape (e.g. forestry or ecological), in construction terms it would be understood to mean specifically the weight force or precisely the force per bearing 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 becomes lighter while it is lying down, both when it is warm and when it is very cold after snowfall: in the first case, snow melts, seeps through the pores and runs off; in the second case, the water sublimates ("evaporates") directly into the air. This is favoured by sunshine and dry air. From a structural point of view, even several metres of dry fresh snow on technically sound roofs are not a threat. What is problematic is heavy snowfall at around to above zero degrees, because this causes very heavy snow to fall by itself, and even more rainfall into high snowpacks. Then large amounts of water can be additionally bound up in the snow cover, and the snow load actually becomes many times higher, which can lead to spontaneous failure of a roof. This can happen within a few hours. Therefore, prolonged cardboard snowfalls and heavy snow that turns into rain are acute crisis scenarios.  Fog frost, term for the deposited precipitation of hoar frost, hoar frost and clear ice. Fog frost is caused by supercooled fog droplets that freeze spontaneously on obstacles whose surface temperature is also below 0ºC. The resulting deposits can form on the surface of obstacles. The resulting deposits can reach great weights, especially at high altitudes in the low mountain ranges, and thus endanger forests, power lines and pylons, especially as high wind speeds often occur during such weather conditions.



Snow is frozen precipitation, usually crystallised in sheets, whose density and weight depend primarily on the air temperature, at the time of snowfall - at the entire atmospheric height - thus... read more »
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HIM - Electronic sensors for the determination of iload and fog frost

Snow is frozen precipitation, usually crystallised in sheets, whose density and weight depend primarily on the air temperature, at the time of snowfall - at the entire atmospheric height - thus also during the lying time: It influences the crystallisation and agglomeration form. Snow forms a normally hexagonal-star-shaped crystal form, which can interlock to form large snowflakes even during snow formation. When lying on the ground, the snow changes into a highly complex structure due to the accumulation of further layers as well as recrystallisation.
Fresh snow has a specific weight of 0.03 (dry freshly fallen snow) to 0.2 (well-set fresh snow without additional water absorption). In terms of pressure, one metre of powder snow corresponds to a column of water about five to ten centimetres high, in the case of cardboard snow (wet snow) it is about 20 cm, i.e. 50-200 litres per square metre of precipitation (water equivalent). A cubic metre of water weighs one tonne (1000 kg), a cubic metre of fresh snow thus 30-200 kg, longer lying snow often much more.Snow load generally acts as a surface load perpendicular to the base area. For static verifications, with regard to the load assumption, it is simplified - and on the safe side - to calculate with wet snow and a weight (specific weight, weight force per volume) of 2 kN/m³, which corresponds approximately to the above-mentioned value for strongly bound fresh snow.
Snow pressure as a general word is synonymous with landscape (e.g. forestry or ecological), in construction terms it would be understood to mean specifically the weight force or precisely the force per bearing 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 becomes lighter while it is lying down, both when it is warm and when it is very cold after snowfall: in the first case, snow melts, seeps through the pores and runs off; in the second case, the water sublimates ("evaporates") directly into the air. This is favoured by sunshine and dry air. From a structural point of view, even several metres of dry fresh snow on technically sound roofs are not a threat. What is problematic is heavy snowfall at around to above zero degrees, because this causes very heavy snow to fall by itself, and even more rainfall into high snowpacks. Then large amounts of water can be additionally bound up in the snow cover, and the snow load actually becomes many times higher, which can lead to spontaneous failure of a roof. This can happen within a few hours. Therefore, prolonged cardboard snowfalls and heavy snow that turns into rain are acute crisis scenarios.  Fog frost, term for the deposited precipitation of hoar frost, hoar frost and clear ice. Fog frost is caused by supercooled fog droplets that freeze spontaneously on obstacles whose surface temperature is also below 0ºC. The resulting deposits can form on the surface of obstacles. The resulting deposits can reach great weights, especially at high altitudes in the low mountain ranges, and thus endanger forests, power lines and pylons, especially as high wind speeds often occur during such weather conditions.



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