Swiss Hail Network – Evaluation

The Mobiliar Lab for Natural Risks is currently investigating the first observations from the Swiss Hail Network Project, a network of 80 automatic hail sensors installed between 2018 and 2020 in the three most hail-prone regions of Switzerland: the Jura, the Napf and Ticino. Those sensors provide new information about the timing of hailfall and hailstones individual impacts, allowing to obtain a time-resolved hail size distribution (HSD). More specifically, the questions we would like to investigate are the following:

  • What is the point (local) duration of hailfalls in Switzerland and when do they happen? Are there differences between regions? How does it compare with existing literature estimates?
  • What is the point time-resolved HSD measured by sensors? Are there similar/different patterns (no patterns) globally and by region?
  • How do sensors observations compare with traditional hailpads observations? What can we learn from this comparison?
  • What are the strengths and potential limitations of automatic hail sensors? How to make best use of them in conjunction with other hail observing systems?
Figure: Composite of 107 significant hail events measured by automatic hail sensors (events with 25 hailstones impacts or more). The blue shading shows the consolidated impact density distribution by diameter since event start. Circles represent the time of the largest recorded impact for each event.