资源环境科技发展态势分析平台

Hail involving very large hailstones (maximum diameter ≥ 4 cm) is rare but is one of the most hazardous weather phenomena in Poland. The most useful of the numerous weather radar reflectivity indicators are automated hail detection algorithms and reflectivity criteria, which can be easily implemented in operational weather warning systems. Since the temperature at which large hail forms is known, the vertically integrated liquid water content (VIL) can be calculated for the corresponding temperature layer. This paper presents four new VIL-based hail indicators using hail formation temperatures determined by the isotherms from ERA5. We compared these indicators with the 8 km Constant Altitude Plan Position Indicator (CAPPI) and the Waldvogel hail detection method by linking the detected cells to ESWD reports. Based on the VILs, we aimed to determine which layer within the VIL integration was the most useful for large hail prediction. In the case of the VILs, the layer between −12 and −25 °C was the best for hail detection. We also analysed the lead times of these indicators to assess their potential for implementation in the operational warning system in Poland. Using data from the European Severe Weather Database and the Polish radar system, we found that most incidents involving very large hailstones were linked to supercell storms with distinctive reflectivity signatures. The best hail indicator was the Waldvogel et al. (1979) hail detection technique, which had a lead time of approximately 17,5 min. The VIL had a near-zero lead time.