Annual and seasonal rainfall trend analysis in Europe and in the Mediterranean area

Wide-ranging researches on climate change, and on its potential, large-scale, environmental and economic consequences, have been carried out during the last decades (Caloiero et al., 2015; Longobardi et al., 2016). One of the most noticeable consequences in a changing climate is the water cycle modification and, in this process, the precipitation plays a key role, which directly affecting human society, economic activities and natural systems. Studies on seasonal and annual precipitation and its trends at local and global scales showed important variations from one area to another one (IPCC, 2013).The present study investigates the rainfall variability in Europe and in the Mediterranean area using a gridded monthly precipitation dataset produced by the Global Precipitation Climatology Centre (GPCC). In particular, the database analysed is the centennial GPCC Full Data Reanalysis of monthly global land-surface precipitation based on 75,000 stations worldwide that features record durations of 10 years or longer. This database contains the monthly totals on a regular grid with a spatial resolution of 0.5° x 0.5° latitude by longitude, with a temporal range from January 1901 until December 2009 (Meyer-Christoffer et al., 2015). In order to determine yearly and seasonal rainfall trends, a statistical analysis was performed. The dataset was analysed for trend, and significance assessed with the Mann-Kendall non-parametric test (Mann, 1945; Kendall, 1962). The trendsslopes were calculated by least square linear fitting. A negative trend of the annual rainfall has been observed in Africa and in the Mediterranean basin. Conversely, a positive trend in the yearly precipitation has been detected in north Europe. The results confirm the evaluations of other studies, carried out on smaller spatial scales, which evidenced marked significant trend only for yearly precipitation.