Analysis of dry events in Calabria (southern Italy)

Drought phenomena are one of the greatest damaging climate events and play a significant role in socio-economic and health terms. The analysis of the main characteristics of drought events (intensity, duration, recurrence probability, spatial extent, etc.) can be useful in order to alleviate the impacts of these phenomena. In this study, the drought features of Calabria (southern Italy) are analysed by means of a long homogeneous database, updated until the most recent months. The drought events have been evaluated on both daily and monthly scale. For the former, the frequency of long dry spells was analysed; for the latter scale, the Standardized Precipitation Index (SPI) has been calculated on several time-ranges. Dry event frequencies were also evaluated using stochastic models by which a high number of synthetic data series has been generated. Moreover, possible trends of drought events have been also evaluated by means of a non-parametric test and graphical approaches. As a result, a general increase in the occurrence frequency of extreme drought events has been detected in the last decades of the past century and at the beginning of the current one. This result was confirmed also by the application of the stochastic approach, which revealed a tendency towards a strong reduction (about 50%) of the return period estimated for long dry spells. Moreover, results of the SPI trend analysis showed a general reduction of the index values, thus evidencing a tendency towards heavier droughts.