Information about the new snow 3-day map (HN 3 gg)

The map is published every day at 10:00 a.m. and shows the new snow that has fallen over the last 3 days (HN 3gg). It is a useful datum for hikers, mountaineers and ski tourers, if compared with the data of new snow at 1 day (see new snow 1-day map), so that they can get an idea of ??the amounts of recent snow, potentially not yet stabilized.

The map shows the new snow amounts cumulated in the last three days through:

- spatialized new snow data, cumulated over three days, obtained from the S3M model (Snow Multidata Mapping and Modeling). S3M uses a dynamic model that describes, in a simplified way, the snowpack evolution, through the snow observations (from automatic weather stations) and the MODIS satellite images (to distinguish snow-free areas from snow-covered ones). Also the manual observations from Modello1 AINEVA (MOD1) affect the result of the S3M model. In fact they are used by ARPA, together with the data coming from the automatic weather stations, for the weekly calculation of the Snow Water Equivalent (SWE). The SWE data is assimilated by the S3M model once a week. S3M runs, since 2009, on a national scale with a spatial resolution of 500x500 meters and time resolution of one hour. The map shows the simulation at 06.00 a.m. The model is operational at the Centro funzionale regionale as part of an agreement signed with the Fondazione Cima. It should be noted that new snow over three days is calculated as the sum of the daily new snow. Due to the constant settling of the snow, normally this cumulative value is greater than the amount of new snow measured once over the entire time interval (72 h);

- the daily manual observations from Modello1 AINEVA (MOD1) concerning the height of new snow (HN) as the cumulative value over the three days of the new snow amounts specified in the daily new snow map. Due to the constant settling of the snow, normally this cumulative value is greater than the amount of new snow measured once over the entire time interval (72 h). Every morning, between 07:00 and 09:00 a.m., the observers measure how many cm of fresh snow have fallen since the last measurement, by using a white colored tablet, in order to limit the effects of irradiation, which is replaced on the snow surface after each measurement. The measurement fields are fixed and are usually located at an altitude between 1000 and 2500 m a.s.l.. If at these altitudes the new snow is wet or if it has rained, less fresh snow is measured than at higher altitudes. The measurements fields are located mainly in flat areas, possibly sheltered from the wind. The observations collected are punctual values: to define the field position the best compromise was sought, but it must be remembered that, because of the extreme variability of the snow cover (due to wind, solar radiation, etc.), the observations can differ significantly from other adjacent areas.

Corresponding map

NB - Only the HN punctual values from MOD1 correctly collected and entered in the relative database are reported on the map and only the ones with the three consecutive surveys required by the map, so the number can vary from day to day. Since the observations are manually detected they are rather reliable, however, the presence of possible errors is not excluded. The acronym N/A (Not Available) is used when computer problems, for which it is not possible to access the data (even if present) of S3M and MOD1, occur.


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