Are meteorological conditions favoring hail precipitation change in Southern Europe? Analysis of the period 1948–2015

Abstract In the context of a warming climate, one of the variables currently under investigation is related to the detection of possible changes in hail precipitation. In this work, we analyze hail frequencies in one of the most affected areas by this phenomenon in Europe, southern France. Here, an extensive hail detection network has been in operation since 1988. In general, the detection of hailfall is very uncertain. To overcome the constraints of scarcity and poor standardization of hail detection and monitoring systems, some relationships between hailstorm occurrence and synoptic, mesoscale or thermodynamic atmospheric characteristics have been proposed in different areas. Therefore, we analyzed meteorological fields at synoptic scale that are related to the formation of hailstorms in the study area, i.e., geopotential height at 500 hPa, sea level pressure, and lapse-rate between 850 and 500 hPa. These fields describe the state of the atmosphere at low and mid levels, and facilitate the evaluation of thermal and dynamic instability. Using the Mann–Kendall test and Sen estimator, we examined trends in the three fields during the period 1948–2015 and their spatial patterns, revealing an evolution toward synoptic environments that favor hail precipitation in the Mediterranean region.