How Saharan dust and elevated convection can produce negative dipole charge structure ?

The LMA network SAETTA has observed thunderstorms from 2014 to 2023. During this period, 54 thunderstorm days with negative dipole charge structures were observed during African dust flow events over the Corsica island, mainly during the warm season. The spatial and temporal distribution of thunderstorm days provided by SAETTA data shows nocturnal events with negative dipole charge structure, without preferential regions (even on land and on sea), while classic thunderstorms over Corsica with normal tripole charge structure occur mainly over mountains in the daytime. In the case of negative dipole events, METEORAGE data show more intense and frequent +CG lightning flashes than classical thunderstorms, and 89.4% of -IC lightning flashes. Furthermore, ERA-5,reanalysis data and radiosonde data exhibit dry and warm low layers, with a temperature inversion near the surface, forcing the triggering of elevated convection. This observation could be a consequence of the radiative impact of Saharan dust. This study shows no evidence for the microphysical impact of aerosols, i.e. the multiplication of ice crystals despite supercooled water droplets. Meteorological data also exhibit intense wind speeds associated with negative dipole thunderstorms. • Observations of elevated convection and negative dipole charge structure for Mediterranean thunderstorms during Saharan dust flows. • Negative dipole thunderstorms are more especially nocturnal events in the north-western Mediterranean basin. • High wind speeds associated with negative dipole thunderstorms occurrence.