Researchers calculate incidence of sunlight in Switzerland

Solar radiation plays an important role in accurate snowmelt forecasts. Keystone-SDA

Researchers in Switzerland have calculated the incidence of sunlight so precisely that even the shadow cast by every single tree is recorded in a new map of where the sun shines and where it doesn't in the Alpine country.

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The data will be used as the basis for research into snowmelt, climate and the water cycle, the WSL Institute for Snow and Avalanche Research revealed on Tuesday.

Solar radiation plays an important role in accurate snowmelt forecasts. Around a third of precipitation in Switzerland falls as snow. The new data therefore helps with flood warnings and planning for hydropower.

For the model, the researchers used high-resolution data from the Federal Office of Topography (swisstopo). According to the researchers, a particular challenge was how to take into account the varying structure of tree canopies, such as in deciduous trees that lose their leaves in winter.

The map depicts solar radiation across the whole of Switzerland with a resolution of ten metres. The data is available for every hour and every day over a full annual cycle. According to Clare Webster of the Snow Hydrology Research Group at the WSL Institute, the dataset has already been incorporated into current research findings.

“We were able to use it to carry out detailed snow simulations for Swiss mountain forests,” the researcher said. This has demonstrated how differently the forest influences the snow cover depending on location and weather.

The data is available to the public on the Envidat data portalExternal link.

Translated from German with AI/gw

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