How is snow depth measured?
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I was wondering how is snow depth measured and how accurate are the values?
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@dorucalinciobanu
Snow depth is computed by weather model and it is the accumulation of old snow + next snow falls, less natural compaction and melting of the snow cover. For this reason this layer shows the snow density too.
Are the values accurate? First the resolution of the ECMWF model is 9km (5.6M). So in mountains it cannot be very accurate, also because the orography model ( i.e. the vertical terrain resolution) used by the weather model is quite coarse too.
Then, after snowfalls, snow layer compacts and its density increases. This factor is difficult to estimate. And finally snow partly melts. In addition the limit between snow and rain is not precise too.
The Snow depth map is interesting to compare a region with another one or to get an idea about the snow depth in the following days. But it's not a way to know the precise snow depth at a location particularly in mountains. In cold countries where snow is not only present in altitude, the accuracy is probably better in non mountainous areas. -
@idefix37 Thank You! But HOW is it measured? If I choose a point with geographic coordinates in the mountain zone it shows me a snow depth. HOW is this value measured or computed?
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@dorucalinciobanu
The snow depths shown in Windy, on the map or by the weather picker at a location, are NOT measured but computed by the weather model. As said above, there are 2 parameters that are considered:
-The thickness of the snow which is the result of the accumulation of snowfall, reduced by melting and evaporation.
-The variation in snow density due to self-compaction.
The calculation is reiterated at each update.Snow depth observed at some weather stations (provided by SYNOP) and extension of snow cover observed by satellites are used in the analysis phase of computation. The observation data is entered into the model to generate initial conditions at each update cycle.
Basically:
https://apps.ecmwf.int/webapps/opencharts/products/medium-snow-sic?base_time=202103071200&projection=opencharts_europe&valid_time=202103151200
And if you need more information:
https://www.grss-ieee.org/wp-content/uploads/2011/07/3_derosnay_IGARSS_20111.pdf
https://journals.ametsoc.org/view/journals/hydr/11/4/2010jhm1249_1.xml -
@idefix37 THANK YOU!!
