Goals of the Project

The project will both advance our understanding as well as test its application in the following three areas:

1. Impact assessment and decision support: Quantification of hail risk and sector-specific impact has not yet been undertaken at a resolution relevant for actual decision making by specific users. Substantial improvements in spatial and temporal resolution expected from the concerted effort in forecasting and modeling of hailstorms (see 2 and 3 just below) will form the basis for high-resolution fully probabilistic risk assessment, including the development of impact-oriented forecasting. For sectors most exposed to hail risk, namely buildings/cars and agriculture, we will co-develop and implement a pre-operational hail impact forecast system by integrating users very early on. To complement this effort on the operational scale, insights in the future evolution of hailstorms in a changing climate will allow to inform sectoral adaptation strategies to strengthen societal resilience against hail risk in future.

2. Technology development: Kilometer-scale weather and climate models have seen dramatic progress in the last 10 years. Such resolutions are able to explicitly resolve (rather than parameterize) key aspects of moist convection and thunderstorms. Technical challenges that need to be addressed relate to (i) the use of next-generation supercomputer architectures with a many-core design using accelerators (e.g., Graphics Processing Units, GPUs), and (ii) coping with the output avalanche of these models. scClim will address these challenges building on progress and expertise established during a previous Sinergia proposal (crCLIM) and profiting from independent ongoing activities in the framework of the Center for Climate Systems Modeling (C2SM; c2sm.ethz.ch). In addition, polarimetric radar data and its space-time structure (e.g., ZDR-columns) will be used to improve the single-polarization estimates of hail size.

3. Process understanding: The relevant processes include local thermo-topographic wind systems and interactions with the synoptic-scale flow. An in-depth process understanding of hailstorms in Switzerland can contribute to improved forecasts, to a better quantification of hail related risk, and to constrain the future occurrence of hailstorms in a warmer climate. Also, a project addressing hail in complex orography complements the impressive body of literature on severe (hail) storms in North America, which develop in a different setting with respect to orography and synoptic scale forcing.

These three areas will for the first time be combined into a comprehensive, seamlessly integrated model chain for hail in Switzerland, from process understanding to model-assisted decision making. In order to do so, we will exploit high-performance hail simulations and provide decision-makers with sector-specific high-resolution information on time scales from hours (warnings) to decades (adaptation, long-term strategic development). To achieve these goals, scClim is structured into five subprojects A-E with the following specific objectives:

Subproject A: Co-development of a hail impact assessment platform for multiple sectors
Subproject B: Hail in weather and climate modeling
Subproject C: Observations of hail, interannual variability and model validation
Subproject D: Modeling hail damage to agriculture
Subproject E: Modeling hail damage to buildings and cars