Analysis of Monthly Rainfall Trend in Calabria (Southern Italy) through the Application of Statistical and Graphical Techniques

One of the most evident consequences of global atmospheric warming is the modification of the water cycle. Precipitation plays a crucial role in the process and its variations can affect water resources, natural environments and human activities. In this paper, an investigation of the temporal rainfall variability in the Calabria region (southern Italy) has been carried out using a homogeneous and gap-filled monthly rainfall dataset of 129 rain gauges with more than 50 years of observation in the period 1951–2006. Possible trends in monthly and annual rainfall values have been detected by means of the Mann–Kendall test and of a new graphical technique (Şen’s method), which allows the trend identification of the low, medium and high values of a series. As a result, a different behavior of both the highest and the lowest rainfall values emerged among the five Rainfall Zones (RZs) that were considered in the analysis. Moreover, from the comparison of the trend methodologies, different trends results (increasing, decreasing, or trendless time series) have been identified. In particular, this study shows that the Şen’s method could be successfully used in the evaluation of peak and low values of data for the trend analysis of rainfall values