Analysis of the characteristics of dry and wet spells in a Mediterranean region

Climate change could increase the risk of future hydrological extremes over large regional areas and trigger further pressure on water resource availability. In this study, the overall characteristics of dry and wet spells during a 56-year period (1951-2006) were analysed in the Calabria region (southern Italy), considering both yearly and seasonal scales. In particular, the mean and maximum lengths of dry/wet spells, the number of dry and wet spells with different lengths, and the contribution of dry/wet spells with different lengths to the total number of dry/wet days have been investigated. The results showed similar behaviour of both dry and wet spells in the spatial distribution of the mean lengths, with a difference between the two opposite sides (Ionian and Tyrrhenian) of the region. In fact, mean values ranging between 6 and 8 days, and higher than 8 days have been detected on the Tyrrhenian and on the Ionian side, respectively. The results regarding the maximum values of the lengths show much higher values of dry spells than the wet ones, and different temporal distributions throughout the year. In particular, with respect to dry spells, in autumn the maximum lengths reached values higher than 200 days, while the longest wet spells have been identified in winter, with a maximum value of 44 consecutive days with rain. The outcomes of this study can be useful for both water resources (with respect to the dry sequences) and risk reduction (regarding the wet spells) management.