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SnowMapper

SnowMapper maps snow across mountain ranges every day. It gives the snow on the ground now, the outlook for the next ten days or so, and how this season compares with past seasons. It runs the same way in every region it covers, from the Alps to the Himalaya. This site explains how to use the dashboards and the science they are built on.

  • Manual

    How to read the map, the forecast, the anomalies, the climatology and the warnings. Start with the quick tour.

  • Science

    How coarse weather data becomes snow at hillslope scale: terrain, downscaling, the snow model, forecasts and satellite data.

  • Known limitations

    What the model gets wrong and by how much. Read this before you rely on a number.

  • Reference

    Domains, variables and units, a glossary and literature references.

What SnowMapper does, in one picture

flowchart LR
    A["ERA5 reanalysis<br/>~31 km, hourly"] --> D
    B["ECMWF IFS forecast<br/>9–25 km, + ensemble"] --> D
    C["Terrain model<br/>DEM, 30–500 m grid"] --> U["10 000 terrain units<br/>(similar elevation, slope,<br/>aspect, sky view)"]
    U --> D["Downscaling<br/>TopoPyScale 2"]
    D --> F["Hourly weather<br/>for every unit"]
    F --> M["Snow model<br/>FSM"]
    M --> P["Daily maps:<br/>SWE, snow depth, runoff…"]
    P --> K["Anomalies vs<br/>multi-year climatology"]
    P --> W["Warnings, meteograms,<br/>validation"]
    S["MODIS / Sentinel-2<br/>snow cover"] -.-> W
  1. Weather in. Global weather data (ERA5 for the past, ECMWF IFS for the forecast) are far too coarse for mountains. A single grid cell can span a valley floor and a 6000 m ridge.
  2. Terrain. The landscape is divided into about 10 000 terrain units: patches of ground with similar elevation, slope, aspect and sky view.
  3. Downscaling. For every unit, every hour, the weather is adjusted to that unit's elevation and exposure: temperature and humidity at the right height, sunshine on the right slope, and rain or snow decided by the wet-bulb temperature.
  4. Snow model. A physically based snow model (FSM) accumulates, compacts and melts the snowpack in each unit, hour by hour.
  5. Maps. The units are painted back onto the terrain grid and become the daily maps you see on the dashboard, alongside forecasts, anomalies and validation against satellites and stations.

The dashboards

All boards are listed on the SnowMapper portal. The regions and their particular setup are in Domains.

Who makes SnowMapper

SnowMapper is developed by Mountain Futures on the open TopoPyScale 2 downscaling engine and the Factorial Snow Model (FSM) by Richard Essery. Partners and funders differ by region and are named on each board's Info tab.