High-resolution spatial analysis of temperature influence on the rainfall regime and extreme precipitation events in...

In the last few years, several works have analyzed rainfall regime changes with the increase of temperature as a result of global warming. These changes, documented mainly in northern Europe, still need to be clarified in the Mediterranean area. Many studies have identified sometimes contradictory trends according to the type of data used, the methodology, and the daily or subdaily types of events. Therefore, an in-depth investigation of the Mediterranean area is required for the definition of more certain future scenarios. In this study, we examined a very large database including >1000 raingauges and thermometers in northern and central Italy to analyze the relationship between temperature and rainfall using the relation Clausius-Clapeyron. Furthermore, we analyzed the relationship between temperature and extreme precipitation events (EPEs, defined as the events higher than the 95th percentile) calculating the temperature anomalies occurred during these events. This large database covers a low rainfall accumulation period (RAP) that allowed us to study the relationship between temperature and rainfall and to distinguish rapid from long events related to rainfall intensity. The results show different relationships between rainfall and temperature in relation to seasons, RAPs, rainfall intensity, and geographical factors. The high spatial density of the database made it possible to identify spatial clusters with homogenous characteristics mainly influenced by geographical factors. With an increase in temperature, the wet season is characterized by a general increase in rainfall with a higher surge for intense and fast events. Instead, the dry season shows a general rainfall decrease for less intense and longer events, but an increase in rapid and more intensive rainfall events. This outcome has further implications involving a future decrease in water availability and an increase of the EPEs, causing an extremization of the climate during the dry season for northern and central Italy.