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

Abstract

Abstract. Climate change projections indicate that extreme snowfall is expected to increase in cold areas, i.e., at high latitudes and/or high elevation, and to decrease in warmer areas, i.e., at mid-latitudes and low elevation. However, the magnitude of these contrasting patterns of change and their precise relations to elevation at the scale of a given mountain range remain poorly 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 on both elevation and time. Specifically, for each massif and four elevation ranges (below 1000, 1000–2000, 2000–3000, 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 in 100-year return levels between 1959 and 2019 equal to +23 % (+32kgm-2) on average at 3500 m and a decrease of −10 % (-7kgm-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 contrasting 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 hazard management in mountain regions.

Snow sensitivity to climate change during compound cold-hot and wet-dry seasons in the Pyrenees

“…The results are consistent with recent snow trends at > 1000 m in the Pyrenees, where increases in the frequency of west circulation weather types since the 1980s triggered positive HS (Serrano-Notivoli et al, 2018;López-Moreno et al, 2020), snow accumulation (Bonsoms et al, 2021a) and winter snow days trends (Buisan et al, 2016). Similar trends have been found in the Alps, where during the last decades an increase of extreme snowfall (> 3000 m; Roux et al, 2021) as well as winter precipitation 100-year return levels has been detected (Rajczak and Schär, 2017).…”

“…The Mediterranean basin is one of the primary climate Hot-Spots of the Earth (Giorgi, 2006), being densely populated (> 500 million of habitants) and affected by an intense anthropogenic activity. Warming across the Mediterranean basin is projected to accelerate for the mid-end 21st century, and temperature is expected to continue higher than the global average during the warm half of the year (e.g., Lionello and Scarascia 2018;Cramer et al, 2018;Knutti and Sedlacek, 2013;Evin et al, 2021;Cos et al, 2022), increasing atmospheric evaporative demands (Vicente-Serrano et al, 2020), drought severity (Tramblay et al, 2020) and implying a waterscarcity scenario over most of the basin (García-Ruiz et al, 2011). Mediterranean mid-latitude mountains, such as the Pyrenees, where this research focuses, are the main runoff-generation zones of the downstream areas (Viviroli and Weingartner, 2004), providing the majority of the water resources for major cities located in the lowlands (Morán-Tejeda et al, 2014).…”

“…For the mid-end 21st century, climate change scenarios over the Pyrenees anticipate a temperature increase of > 1 to 4 ºC, and positive (negative) precipitation trends (~ 10 %, respect the 1980 -2010 period) for the eastern (western) sectors of the range during winter and spring (Amblar-Frances et al, 2020). Therefore, snow evolution in the high elevations of the range is subject to major unknows, since winter snow accumulation is ruled by precipitation (e.g., López-Moreno et al, 2008), and Mediterranean basin winter precipitation projections are subject to large uncertainties, due to a large contribution of internal variability of the latter (up to 80 % of the total variance; Evin et al, 2021).…”

Development and validation using ground truth of a method to identify potential release areas of snow avalanches based on watershed delineation

“…In this paper, we focus on the French Alps and its classical segmentation into 23 massifs for snow-climate reanalyses and operational snow avalanche forecasting (e.g., 2009a;2009b;Evin et al, 2021).…”

“…This will improve our understanding of PRAs characteristics within the whole French Alps, and possibly allow 550 identifying groups of massifs with common properties in terms of PRAs. This information could also be used, combined with available extreme snowfall/snow depth estimates (Gaume et al, 2013;Le Roux et al, 2021), for a large-scale mapping of avalanche hazard and risk in the French Alps using simulation tools, as already done in other countries such as Switzerland (e.g. Bühler et al, 2018;.…”