An historical flash drought analysis in Sicily based on ERA5 Reanalysis evapotranspiration and soil moisture data

Sicily copes periodically with the challenge of drought events, impacting water resources management, as well as agricultural and environmental landscapes. While the area is well studied regarding traditional slow-evolving droughts, studies on flash droughts are lacking. This study delves into the historical analysis of flash drought events in Sicily, characterized by their abrupt onset and severity.  Specifically, we carry out our analysis based on ERA5-Land Reanalysis daily evapotranspiration and soil moisture data, covering the period 1950-2023. First, a comparison of ERA5-Land Reanalysis evapotranspiration with reference evapotranspiration computed from observational series is carried out. Then the Evaporative Demand Drought Index (EDDI) is computed from the Reanalysis evapotranspiration series, at various temporal scales. The EDDI index is then analysed in combination with soil moisture series at various soil depths, to corroborate the identification of the onset of past historical flash drought events. A specific focus in devoted to a heat wave occurring during July 2023, showing the severity of this event. The study provides preliminary insights for a clearer development of criteria for flash drought identification in the Mediterranean area.