Statistical analysis of inter-arrival times of rainfall events for Italian Sub-Alpine and Mediterranean areas

In this work a set of time-series of inter-arrival times of rainfall events, at daily scale, was analysed,with the aim to verify the issue of increasing duration of dry periods. The set consists of 12 time-seriesrecorded at rain gauges in 1926–2005, six of them belong to an Italian Sub-Alpine area (Piedmont) and six toa Mediterranean one (Sicily). In order to overcome the problem related to limited sample size for high valuesof inter-arrival times, the discrete probability polylog-series distribution was used to fit the empirical data frompartial (20 yr) time-series. Moreover, a simple qualitative trend analysis was applied to some high quantiles ofinter-arrival times as well as to the average extent of rain clusters. The preliminary analysis seems to confirmthe issue of increasing duration of dry periods for both environments, which is limited to the “cold” season.