Hail Characteristics and Cloud Seeding Effect for Hail Suppression in Central Macedonia, Greece

The Greek National Hail Suppression Program (GNHSP) is an airborne cloud seeding program, running since 1984 under the auspices of the Hellenic Agricultural Insurance Organization (ELGA). Hail data are provided by a network of 154 hailpads installed in the project Area 1 (Hmathia-Pella-Pieria-Kikis-Thessaloniki) of the GNHSP, for a 28-year period (1984-15) from April to September. A large variability in hail occurrence is determined in both spatial and temporal scales. Spatial analysis indicated hailfall maxima close to the western mountain barriers and northern higher terrain areas. Considering inter-annual distribution, a significant increase in both hail days and hailpad number recorded hail is most pronounced for the last decade, implying a possible climatic change influence. An assessment of cloud seeding effect was based on hail data from seeded compared to no seeded hailstorms. The results indicated a positive effect in hail suppression, confirming cloud seeding hypothesis, with seeded hailstorms generally producing less dense hailfalls and a decrease of larger hailstones frequency.