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Science

SnowMapper answers one question: how much snow is on the ground at every point of a mountain range, today and over the coming days? The scale mismatch makes this hard. Global weather models work on grid cells of 9–31 km. Snow varies over hundreds of metres, with elevation, slope and sun exposure.

SnowMapper bridges the gap in four steps, all run every day:

flowchart TB
    subgraph IN [Inputs]
      E[ERA5 reanalysis] 
      I[ECMWF IFS / ENS forecast]
      T[Digital elevation model]
    end
    T --> S[1. Terrain units<br/>TopoSUB clustering]
    E --> D[2. Downscaling<br/>TopoSCALE / TPS2]
    I --> D
    S --> D
    D --> M[3. Snow model<br/>FSM]
    M --> P[4. Products<br/>maps · anomalies · warnings]
    O[MODIS · Sentinel-2 · stations] -.validation / assimilation.-> M
Step Page In one sentence
1 Terrain and spatial units Group the landscape into ~10 000 units of similar terrain, so the physics runs 10 000 times instead of millions.
2 Meteorological downscaling Adjust coarse weather to each unit's elevation, slope, aspect and horizon, hour by hour.
3 Snow model Run an energy-balance snow model on each unit's weather.
4a Forecasts Continue the analysis with deterministic and ensemble forecasts.
4b Climatology and anomalies Re-run past seasons to know what normal looks like.
— Satellite and data assimilation Check, and in some regions correct, the model with observations.
— Known limitations What goes wrong, measured.

Design choices

  • Physics, not statistics. Every map comes from conservation of mass and energy. No local training data are needed, so the method transfers to data-poor regions. The trade-off is that errors in the input weather pass through.
  • Same engine everywhere. All regions use the same code. Differences between boards come from their configuration (domain, resolution, forecast source), listed under Domains.
  • Hourly physics, daily maps. The model runs hourly, so day–night melt and refreeze are resolved. Maps show daily values.
  • Open foundations. The downscaling engine (TopoPyScale 2) and the snow model (FSM) are open source. Their scientific basis is published. See References.