The measure of the snow, both fresh and accumulated on the ground, is very important in the Alpine context. It is an essential component of alpine meteorology and climatology, characterizing the landscape (and everything related with it) for the winter months.
The snow cover varies significantly from year to year, both in maximum thickness and in temporal extension. These aspects are fascinating to study, and thanks to the automatic weather stations, they are also much easier to record.
Today, the most widespread network of snow surveys in the Piedmont area is that of the ARPA, which has about 80 stations located mainly in the mountains, but also with some measurement points on the plains.
The automatic measurements take place with ultrasonic snow gauges, consisting of a pair of transducers: an emitter and a receiver. Its operating principle is very similar to that of the sonic anemometer knowing the speed of sound (corrected with the temperature), the snow gauge calculates the height of the snow from the flight time of the sound package (round trip) reflected from the surface of the snow.
On the side and above, you can see the snow metre installed at the Alpe Veglia station, this instrument was built in our laboratories and tested in the Alpe Veglia campaign.
The uncertainty associated with this instrument is 1.5-4 cm, and its maximum range of 5 meters.
Manual snow measurements, on the other hand, require an operator on site every day, in order to measure the fresh snow of each day deposited on a clean wooden board every day. Alternatively, it is possible to obtain the height of the snow with the snow rods (like the one in the initial photo), in which the layer of snow on the ground is measured, combining fresh, transformed, compacted snow and also that carried by the wind.
The greatest difficulty is therefore to choose the best site for the measurement of the snow, so that it is not too much or too little sheltered from the wind, and too much in the shade (thus reducing the effect of the sun).
In the case of the Alpe Veglia station, the place identified by the ARPA is in the larch grove, to limit wind transport, while the micrometeorological station is in an open field, to better measure the heat flows and turbulence. The data of snow is beneficial to know how "high" the instruments are compared to the ground.
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