A rainfall trend analysis for the assessment of climate change in Friuli-Venezia Giulia (north-eastern Italy)

Climate change is expected to impact on rainfall variability and lead to a substantial modification in rainfall amounts. In this study, the spatiotemporal variability of rainfall in Friuli-Venezia Giulia (north-eastern Italy) has been evaluated by means of 67 monthly series for the period 1940–2011. In particular, in order to analyse possible trends in rainfall series, two nonparametric tests for trend detection have been used. Moreover, the monthly rainfall distribution throughout the year was also investigated by means of the precipitation concentration index (PCI). In addition, a correlation analysis has been performed between seasonal rainfall and four of the most important teleconnection indices, i.e. the Western Mediterranean Oscillation Index (WeMOI), the Oceanic Niño Index (ONI), the North Atlantic Oscillation Index (NAOI) and the Arctic Oscillation Index (AOI). The results evidenced a reduction in rainfall amount, mainly detected in the spring and the summer months, and a positive trend in the PCI. The latter indicates a tendency towards a more seasonal rainfall distribution in the Friuli- Venezia Giulia region throughout the year. Finally, the WeMO was identified as the most relevant teleconnection over all of Friuli-Venezia Giulia in the different seasons.