Extended-range warnings for heatwaves in Switzerland

Heatwaves in Switzerland have various impacts on human health and ecosystems. Moreover, heat extremes might act as final triggers for high-Alpine hazards such as glacier break-offs and rockfalls, because they can accelerate the slowly growing disturbance of the Alpine permafrost layer due to climate warming. Heatwaves often occur concurrently with drought, which can impact agriculture, reduce lake and river shipping due to low water levels, and reduce nuclear power generation due to shortage of cooling water. As heatwaves have become and are expected to become even more common with climate change, it is crucial to predict their occurrence ahead of time and to issue warnings for stakeholders and the general public. The goal of this interdisciplinary project is, therefore, to assess the potential of heatwave prediction and warnings for Switzerland on timescales up to several weeks. The project consists of two parallel branches: on the one hand, we investigate if the forecast skill horizon for Switzerland can be extended by predicting heatwaves via statistical downscaling from larger-scale weather patterns compared to the prediction based on direct model output on a grid point level. On the other hand, we evaluate the potential benefits of early warning products for sectors that are directly linked to human lives and livelihoods. One focus is on predicting heat-related mortality by coupling a statistical temperature-mortality model to extended-range temperature forecasts. Another focus is on better understanding and predicting the penetration of heatwaves into Alpine glaciers, rocks, and sediments, which might ultimately support early-warning systems for heat-related high-Alpine hazards. The aim of our presentation is to introduce the multifaceted project in more detail and to provide some first results from the different branches.