Snow depth oddity
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Snow depth in Europe is shown as 3m deep in sharp-edged blocks
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@chris-bolton Hello, would you like to report any issue? You can change the units by clicking on "cm" unit.
Korina
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As I read that display, it's showing clearly defined patches of lying snow, 3m deep, with quite sharply defined and sometimes straight edges that don't follow the terrain. That's not what I expect to see at this time of year, snow should be mostly on the mountains and with the depth tapering off gradually. If it showed 3cm of snow like that, fine, but 3m is a typical winter accumulation. So I think there's an error.
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@chris-bolton Hello, as you can see on the screenshots, the snow patches are located on the top of Swiss Alps, therefore the snow depth makes sense. Furthermore, the layer shows forecasted values, actual snow depts might be influenced by many factors like orography, cities and so on.
Korina
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@korina
Thanks - if you're happy with it, OK. I thought 'new snow' was forecast (and the display shows how many days accumulation), and 'snow depth' was historic accumulation in the model, as there's no timescale on the display. It is in the general area of the Alps, but the patches cover the valleys as well as the mountains so I though it was a modelling artifact.Happy to close it out as bug, if you wish.
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@chris-bolton
Global models, even ECMWF model with 9 km resolution, are quite bad in mountains. The 9km distance between grid points and the interpolation between them cannot give a realistic view of weather in these areas. In addition the topographic model that global models use is very coarse. For example the temperature shown at top of Mont-Blanc 4800m is almost the same as that in the valley, at Chamonix 1100m.
Anyway I agree with you the Snow depth layer gives strange pictures. I don’t remember to have seen that in the past. We will see later in the season. -
@idefix37 - thanks, understood.
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@chris-bolton Furthermore, Snow depth is not historic accumulation, but snow density/depth in the next days. New snow layer is total snow accumulation in next hours or days.
Korina
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@korina said in Snow depth oddity:
Snow depth is not historic accumulation, but snow density/depth in the next days.
Please could you confirm that the ‘Snow depth’ forecast is the accumulation of old snow ie before the forecast date plus the next falls and the natural compacting of the snow cover.
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@idefix37 @Chris-Bolton Detailed description - https://apps.ecmwf.int/codes/grib/param-db/?id=141
Korina
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@korina
So the ‘Snow depth’ is the past accumulation + the predicted snowfalls.
More information here:
https://apps.ecmwf.int/webapps/opencharts/products/medium-snow-sic?base_time=202110220000&projection=opencharts_europe&valid_time=202110220000This map shows the same ‘blocks’ as in Windy over the Alps.
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@idefix37 said in Snow depth oddity:
past accumulation + the predicted snowfalls.
Snow depth is layer indicating depth of a laying snow, it is based on snow density and amount of water in precipitation.
