The snowfall risk assesses the hazard posed by extreme snowfall, which can overload structures (snow load) and disrupt operations. It is measured through the annual maximum daily snowfall (in water equivalent, SWE), whose statistical rarity is estimated using the return period: the rarer the event, the higher the risk.
Indicator. Annual maximum daily snowfall, in mm of water equivalent (SWE), expressed as a return period.
Data. CMIP6 variable prsn (snowfall flux, kg m⁻² s⁻¹, converted to mm/day SWE) from the Copernicus Climate Data Store (CDS); historical series and future projections. Scenarios: SSP1-2.6 / SSP2-4.5 / SSP3-7.0 / SSP5-8.5.
Calculation.
(1) A GEV (Generalized Extreme Value) distribution is fitted to the historical annual maxima of daily snowfall.
(2) For each scenario and future year, the multi-model maximum is taken and its return period is computed via the GEV survival function, capped at 250 years.
(3) The return period is classified into levels.
Thresholds → level A–F.
• return period < 5 years → A
• 5–20 → B
• 20–50 → C
• 50–100 → D
• 100–250 → E
• ≥ 250 years → F.
From physical to impact. The physical level (A–F) is combined with the production process's sensitivity through the 5×5 risk matrix → impact level; the damage curve converts the level into a damage factor, from which the economic value at risk is derived.
Sources.
• [Copernicus Climate Data Store (CDS)](Copernicus Climate Data Store (CDS))
• [Contrasting responses of mean and extreme snowfall to climate change](Contrasting responses of mean and extreme snowfall to climate change)
• [Projected 21st century snowfall changes over the French Alps and related uncertainties](Projected 21st century snowfall changes over the French Alps and related uncertainties)
• [An Introduction to Statistical Modeling of Extreme Values](An Introduction to Statistical Modeling of Extreme Values).