Trends in Swiss Alpine snow days: The role of local‐ and large‐scale climate variability

Abstract

[1] Swiss Alpine snow cover is varying substantially on interannual to decadal time scales. In the late 20th century decreases in snow days (SD) have been observed for stations below 1300 m asl. A regression model is used in this work to quantify the importance of mean temperature and precipitation as well as large-scale climate variability in order to explain the observed trends. Both, local-and largescale models account for a modest fraction of the observed seasonal variability. Results suggest that the recent decrease in low altitude snow cover can mainly be attributed to an increase in temperature. Differences are found for northern and southern Switzerland concerning the influence of large-scale climate patterns. In contrast to southern Alpine regions, northern Alpine interannual SD variability is almost unaffected by the North Atlantic Oscillation (NAO). Decadal trends, however, can be explained via temperature only by a model that includes the explanatory variable NAO.

Winter severity and snowiness and their multiannual variability in the Karkonosze Mountains and Jizera Mountains

“…The pattern found is consistent with the results obtained for Europe, where in the second half of the 1951-2010 period, an increase in the frequency of exceptionally mild winters was observed at the expense of exceptionally cold ones (Twardosz and Kossowska-Cezak 2016). In the last two or three decades, an increase in the frequency of warm winters has also been recorded in the Swiss Alps (Scherrer et al 2004;Marty 2008) and the USA (Mayes Boustead et al 2015).…”

“…The conditions were very similar during the winters of 2013/2014 and 2015/2016, which at the same time were also exceptionally warm winters. The decrease in depth of snow cover and its retention time since the late 1980s has also been characteristic of stations situated at lower altitudes in the Alps (Laternser and Schneebeli 2003;Scherrer et al 2004;Marty 2011). That trend was noticeable at stations both on the northern and southern slopes of the Swiss Alps (Marty 2008).…”

“…in the Swiss Alps at the end of the twentieth century was also due to the increase in air temperature and macrocirculation associated with the North Atlantic Oscillation (NAO). NAO is the factor that accounts for the difference in numbers of days with snow cover between the northern and southern slopes of the Alps (Scherrer et al 2004).…”

Long‐term trend analysis of aerosol variables at the high‐alpine site Jungfraujoch

“…Sen's slope estimates of the hemispheric backscattering coefficients at three wavelengths (black circle for l = 450 nm, black square for l = 550 nm, and black triangle for l = 700 nm) with the upper and lower confidence limits for the hemispheric backscattering ratio at 700 nm in gray. [44] The number of snow days in Switzerland from 1980 to 1999 decreased (mean maximal slope depending of the measurement site is of 3 -4 days yr À1 ) for elevations below 1300 m asl due to a temperature increase [Scherrer et al, 2004]. A decrease of snow coverage could decrease the surface albedo and increase thermal convection; this effect can be considered as a secondary effect (positive feedback mechanism) of a temperature increase.…”

Inter-annual variations of snow days over Switzerland from 2000–2010 derived from MODIS satellite data

“…Elsasser and Messerli, 2001;Abegg et al, 2007;Uhlmann et al, 2009). Therefore, ground-based monitoring of the snow cover has a long tradition in Switzerland and a number of studies have been published over the last years, focusing on its temporal variability and long-term trend (Beniston, 1997;Laternser and Schneebeli, 2003;Scherrer et al, 2004;Scherrer and Appenzeller, 2006;Marty, 2008). Overall, these results describe a decrease of the alpine snow pack since the mid 1980's especially at lower altitudes which is linked to an increase of local winter temperatures (Scherrer et al, 2012).…”