Abstract
Abstract. The goal of this work is to investigate and explain recent changes in total and maximum yearly snowfall from daily data in light of current global warming or the interdecadal variability of atmospheric circulation. We focus on the period 1979–2018 and compare two different datasets: the ERA5 reanalysis data and the E-OBSv20.0 data, where snowfall is identified from rainfall by applying a threshold to temperature. We compute changes as differences from quantities computed for the periods 1999–2018 and 1979–1998. On the one hand, we show that the decline in average snowfall observed in almost all European regions is coherent with previous findings and can be linked to global warming. On the other hand, we observe contrasting changes in maxima and sometimes disagreement in the sign of changes in the two datasets. Coherent positive trends are found for a few countries in the Balkans. These have been investigated in details by looking at modifications in the atmospheric weather patterns as well as local thermodynamic factors concurring to large snowfall events. We link these changes to the stronger prevalence of Atlantic Ridge or blocking patterns associated with deeper cyclonic structures over the Adriatic and Tyrrhenian seas. These cyclones find warmer surfaces and large availability of humidity and convective available potential energy (CAPE), thus producing large snowfall amounts, enhanced by the Stau effect on the Balkan topography.
Highlights
Heavy snowfalls can have a great impact on economy and society
We have identified a robust signal in the general decrease in the yearly total snowfall, in particular for northern and western Europe
Changes are more contrasted: negative changes persist over western Europe, but in the proximity of the Mediterranean Sea, we have identified a certain number of countries showing positive changes
Summary
Heavy snowfalls can have a great impact on economy and society. In January 2017, a cold spell affected most of eastern and central Europe and part of southern Europe, causing the death of at least 60 people. Two further recent examples of snowfalls affecting large populated areas are the February–March 2012 snowstorm in northern Italy, with up to 50 cm of snowfall measured in Bologna (Bisci et al, 2012), and the winter 2018 snowstorm Emma, which affected the UK with up to 40 cm of snowfall in Wales and the disruption of air and rail transportation in the London, Manchester and Liverpool areas (Tonks, 2018) Besides their cost in terms of societal and economical impacts, these extreme events are often invoked by climate change denial groups to mystify the public opinion (Revkin, 2008), and it is important to understand why, in an undeniable context of climate change, we do not observe a sharp decrease in their frequency and intensity.
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