Operational radar hail detection algorithms at MeteoSwiss: quality assessment and improvement

In the project "Hail Climate Switzerland", MeteoSwiss, in collaboration with partners from various sectors, has created new products for assessing the hail hazard in Switzerland. These include a new generation of radar hail data, which has been extensively quality checked and reprocessed within the scope of the project. Based on these data, maps and statistics of the monthly and annual number of hail days of different intensities as well as hailstone sizes are produced and made available to the public. Furthermore, using a probability-based resampling approach, return values of hailstone sizes within the Swiss radar domain were computed in high spatial resolution for different return periods. This document describes the radar hail products of the Swiss weather radar network. It focuses on the quality assessment and improvement of the existing operational radar hail detection algorithms at MeteoSwiss that form the basis for the new hail statistics. Further information on the new products and their interpretation can be found in the Technical Report by Schröer et al. (2022).