Identification of convective precipitation events through lightning data in a Mediterranean area

Nowadays, studying heavy rainfall events, characterized by significant rainfall depth concentrated in short durations, and by the presence of lightning, downbursts, and hail, is extremely important. The increasing attention to these phenomena is due to the fact that they may determine serious impacts on the population, economic activities, and the environment. Among heavy rainfall events, high-intensity and short-duration ones, are usually associated with the occurrence of convective cells.

Since these events have been occurring in a more frequent way over the last two decades as a climate change effect and the Mediterranean area is considered one of the most prone areas to this type of event, this study focuses on the identification of heavy rainfall over Sicily, i.e., the biggest island of the Mediterranean Sea. The high-resolution rainfall time series (i.e., 10 minutes) here analyzed have been collected by the rain gauge network of the Servizio Informativo Agrometeorologico Siciliano (SIAS) within the period 2002 - 2021.

Given that convective cells are usually characterized by high lightning activity, their detection has been carried out by means of a lightning dataset of Blitzortung, providing the location and time of lightning strikes for all of Europe on a daily scale since 2015. To reach this goal, different searching radii centred on the rain gauges and some conditions to weigh the distance between lightning strikes to the gauge, have been considered. This allowed exploring how far the lightning activity developed from the rain gauge, where rainfall is recorded.

The detection of convective precipitation through lightning data has been then improved by using some reanalysis data, such as the Convective Available Potential Energy (CAPE), and the K-Index, from the ERA-5 database of the European Centre for Medium-Range Weather Forecasts (ECMWF).