Preprints
https://doi.org/10.5194/tc-2021-64
https://doi.org/10.5194/tc-2021-64

  01 Mar 2021

01 Mar 2021

Review status: this preprint is currently under review for the journal TC.

Elevation-dependent trends in extreme snowfall in the French Alps from 1959 to 2019

Erwan Le Roux1, Guillaume Evin1, Nicolas Eckert1, Juliette Blanchet2, and Samuel Morin3 Erwan Le Roux et al.
  • 1Univ. Grenoble Alpes, INRAE, UR ETNA, Grenoble, France
  • 2Univ. Grenoble Alpes, Grenoble INP, CNRS, IRD, IGE, Grenoble, France
  • 3Univ. Grenoble Alpes, Univ. Toulouse, Météo France, CNRS, CNRM, CEN, Grenoble, France

Abstract. Climate change projections indicate that extreme snowfall are expected to increase in cold areas, i.e. at high latitude and/or high elevation, and to decrease in warmer areas, i.e. at mid-latitude and low elevation. However, the magnitude of these contrasted patterns of change and their precise relations to elevation at the scale of a given mountain range remain ill-known. This study analyzes annual maxima of daily snowfall based on the SAFRAN reanalysis spanning the time period 1959–2019, and provided within 23 massifs in the French Alps every 300 m of elevation. We estimate temporal trends in 100-year return levels with non-stationary extreme value models that depend both on elevation and time. Specifically, for each massif and four elevation ranges (below 1000 m, 1000–2000 m, 2000–3000 m and above 3000 m), temporal trends are estimated with the best extreme value models selected on the basis of the Akaike information criterion. Our results show that a majority of trends are decreasing below 2000 m and increasing above 2000 m. Quantitatively, we find an increase of 100-year return levels between 1959 and 2019 equal to +23 % (+32 kg m−2) on average at 3500 m, and a decrease of −10 % (−7 kg m−2) on average at 500 m. However, for the four elevation ranges, we find both decreasing and increasing trends depending on location. In particular, we observe a spatially contrasted pattern, exemplified at 2500 m: 100-year return levels have decreased in the north of the French Alps while they have increased in the south which may result from interactions between the overall warming trend and circulation patterns. This study has implications for natural hazards management in mountain regions.

Erwan Le Roux et al.

Status: open (until 26 Apr 2021)

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Erwan Le Roux et al.

Erwan Le Roux et al.

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Short summary
Extreme snowfall can cause major natural hazard (avalanche, winter storms) that can generate casualties and economic damages. In the French Alps, we show that between 1959 and 2019 extreme snowfall have mainly decreased below 2000 m of elevation and increased above 2000 m. At 2500 m, we find a contrasted pattern: extreme snowfall have decreased in the north, while increased in the south. This pattern might be related to increasing trends in extreme snowfall observed near the Mediterranean Sea.