Institute of Geography

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Windstorms in Switzerland since 1859

Windstorms are among the major natural hazards in Switzerland, with large damage potential for infrastructure, buildings and forests. Profound knowledge about high-impact windstorms is needed for risk mitigation, e.g., in the field of forest management or construction standards. Specifically, research must consider the generation, the intensity and frequency as well as spatial characteristics of high-impact windstorms in Switzerland. However, such research is limited by the fact that high-resolution wind data and damage statistics mostly span recent decades only. Hence, it is desirable to dispose of a validated catalog of high-impact windstorms in Switzerland over an extended period of time. In addition, numerical case studies of historical events are required on a regional level to better understand synoptic to local weather patterns. This can be conducted by use of the novel 20th Century Reanalysis (20CR), which delivers 3-dimensional information about the state of the atmosphere reaching back to 1871 in relatively good temporal, but rather poor spatial resolution. Smaller-scale wind information can be simulated by dynamical downscaling, i.e., by use of a meso-scale numerical weather forecast model (WRF).

The main objective of the project is to extend historical wind information both in time and space. A first milestone includes the production of an extended catalog of historical high-impact windstorms in Switzerland reaching back to the mid-19th century and validate it against independent wind- and damage-based information. This set of windstorms can then be further analyzed by use of 20CR and WRF to demonstrate the power and limitations of downscaling, e.g., regarding spatial reflection of storm losses, or to address the meteorological particularities of windstorm types found in the catalog. Changes over time and space in the weather patterns associated to high-impact windstorms can be analyzed using weather types in particular. This could furthermore allow for future projections of such changes.

Contemporary postcard depicting a foehn storm over Lake Lucerne
Foehn storm on 1925-02-15. Left: instantaneous wind field from WRF donwscaling at 14h in m/s. Right: normalized estimates of windfall timber and losses to buildings from literature review.

Peter Stucki, Stefan Brönnimann, Olivia Martius, Christoph Welker, Ralph Rickli, Silke Dierer, David N. Bresch, Gilbert P. Compo, and Prashant D. Sardeshmukh (2015) Dynamical Downscaling and Loss Modeling for the Reconstruction of Historical Weather Extremes and Their Impacts: A Severe Foehn Storm in 1925. Bull. Amer. Meteor. Soc., 96, 1233–1241. doi: 10.1175/BAMS-D-14-00041.1.

Brönnimann, S., Martius, O. and Dierer, S. (2014) Die Wetter-Zeitmaschine. Physik in unserer Zeit, 45, 84–89. doi: 10.1002/piuz.201301351.

Stucki, P., Brönnimann, S., Martius, O. , Welker, C., Imhof, M., von Wattenwyl, N., and Philipp, N. (2014) A catalog of high-impact windstorms in Switzerland since 1859. Nat. Hazards Earth Syst. Sci., 14, 2867–2882. doi:10.5194/nhess-14-2867-2014.