Hail Hazard in the Mediterranean (H2Med)

How does climate change impact extreme events and which is the future change of their dynamics? How will the ongoing and future changing climate control the evolution and intensification of severe storms? These are among the most frequent and significant questions for the scientific community, stakeholders and decision-making structures. The project tackles these open issues by investigating hailstorms in the Mediterranean region through the synergistic application of satellite observations, meteorological reanalysis and climatic modelling. Focusing on determining the atmospheric variables most relevant for the formation and intensification of hail-bearing storms, we delineate specific metrics describing the hail formation potentially applicable at operational level. The proposal stems from the 22-yearlong database of hail episodes described by Laviola et al. (2022), whereby events associated with large and extreme hail (above 2 and 10 cm in diameter, respectively) were preliminarily identified and shown to be on a 30% increase trend. Extending and refining this climatology at daily scale, the large-scale and mesoscale atmospheric scenarios that trigger hail events in the central Mediterranean area are investigated through a cluster analysis with the use of meteorological reanalysis data in the recent past. Hail-prone conditions are associated with the optimization of a hail-proxy index based on environmental variables extracted from global and regional reanalysis products. Such index and the reference hail-prone conditions are then be investigated in the ensemble of climate model projections to outline the future evolution of hail-precursors triggering and sustaining deep convection over the Mediterranean basin to the end of the century. This investigation will be also exploited to identify the environmental key variables controlling hail hazards in the recent past, and prospect future changes of storm extremization. The first-year results presented in this work delineate a new paradigm of knowledge for better understanding the effects of climate change on hailstorms by using hail-bearing convective systems as a driver for evaluating the potential impact of future changes in the Mediterranean basin. 

Reference
Laviola S., G. Monte, E. Cattani, V. Levizzani, 2022: Hail Climatology in the Mediterranean Basin Using the GPM Constellation (1999-2021). Remote Sensing, 14(17), 4320.  https://doi.org/10.3390/rs14174320