Snowfall in the Alps: Evaluation and projections based on the EURO-CORDEX regional climate models
Prisco Frei1, Sven Kotlarski2, Mark A. Liniger2, and Christoph Schär11Institute for Atmospheric and Climate Sciences, ETH Zurich, 8006, Zurich, Switzerland 2Federal Office of Meteorology and Climatology, MeteoSwiss, 8058 Zurich-Airport, Switzerland
Received: 15 Jan 2017 – Accepted for review: 21 Feb 2017 – Discussion started: 27 Feb 2017
Abstract. Twenty-first century snowfall changes over the European Alps are assessed based on high-resolution regional climate model (RCM) data made available through the EURO-CORDEX initiative. Fourteen different combinations of global and regional climate models with a target resolution of 12 km, and two different emission scenarios are considered. A newly developed method to separate snowfall from total precipitation based on near-surface temperature conditions and accounting for subgrid topographic variability is employed. The evaluation of the simulated snowfall amounts against an observation-based reference indicates the ability of RCMs to capture the main characteristics of the snowfall seasonal cycle and its elevation dependency, but also reveals considerable positive biases especially at high elevations. These biases can partly be removed by the application of a dedicated RCM bias correction that separately considers temperature and precipitation biases.
Snowfall projections reveal a robust signal of decreasing snowfall amounts over most parts of the Alps for both emission scenarios. Domain and multimodel-mean decreases of mean September-May snowfall by the end of the century amount to −25 % and −45 % for RCP4.5 and RCP8.5, respectively. Snowfall in low-lying areas in the Alpine forelands could be reduced by more than −80 %. These decreases are driven by the projected warming and are strongly connected to an important decrease of snowfall frequency and snowfall fraction and are also apparent for heavy snowfall events. In contrast, high-elevation regions could experience slight snowfall increases in mid-winter for both emission scenarios despite the general decrease of the snowfall fraction. These increases in mean and heavy snowfall can be explained by a general increase of winter precipitation and by the fact that, with increasing temperatures, climatologically cold areas are shifted into a temperature interval which favours higher snowfall intensities.
Frei, P., Kotlarski, S., Liniger, M. A., and Schär, C.: Snowfall in the Alps: Evaluation and projections based on the EURO-CORDEX regional climate models, The Cryosphere Discuss., doi:10.5194/tc-2017-7, in review, 2017.