## 3 Results
### Precipitation Trends  
Among the various precipitation trends, along with their intensities, analyzed in this work (as described in Section 2.3), significant ones are shown here, which may give indications of what precipitation trends might look similar in the years to come. First, trends related to the Paterno locality are shown, and then later those related to Busachi. Figure 3 shows the annual cumulative precipitation trends for the Sicilian location. From Figure 3 it would appear that although the trend falls within a given statistical variability over the last twenty years, starting in 2014 there seem to be more frequent years when precipitation is low. It is useful then to analyze seasonal trends to understand whether precipitation trends have seasonal sensitivity, hence Figure 4a,b are shown, for the Paterno case study. Figure 4: Seasonal cumulative precipitation trends: (**a**) in winter and autumn, (**b**) in spring and summer, for the Paterno case study. Figure 3: Trend of cumulative annual precipitation (mm) over the past twenty years (2002–2021) for the Paterno case study. From the above figures, the cumulative amount of winter precipitation has experienced a marked reduction, portending dry spells in future years this season that could impact energy production from hydroelectric plants afferent to the Paterno catchment. Cumulative autumn precipitation has experienced an increase over the past twenty years, although with a different slope than in winter. Regarding the spring trend, a reduction can be observed from 2011 onwards, but without a marked trend as observed in winter and autumn. Finally, a decreasing trend is noted in summer, with 2018 experiencing a particularly rainy summer (probably an outlier). In addition to the cumulative amount of seasonal and annual precipitation, it is useful to analyze trends in hourly intense precipitation events across seasons and years. Figure 5 shows annual, winter, and autumn trends of heavy precipitation. The summer trend is not shown being that in twenty years there has been no intense hourly rainfall, while the spring trend is not shown because the amount of data available does not allow inferring any trend for this season. From Figure 5, in the last twenty years, the number of annual events with heavy precipitation seems to represent an increasing trend. Specifically, looking at the data from 2002 to 2010, there have been three years in which no intense precipitation occurred in any hour, while from 2010 until 2021 only one year (2016) recorded zero hourly intense precipitation. On the other hand, looking at the seasonal trend of heavy hourly precipitation, winter turns out to be the season with the highest density of hours with heavy precipitation, which from 2010 onward seems to have decreased compared to previous years. In contrast, the autumn pattern shows an increasing trend, which is likely to maintain this slope in the next years. A peak in the number of intense precipitation occurred in 2003: above-average air temperatures in the summer of 2003 probably led to an increase in the amount of water the atmosphere can hold, and thus to more frequent intense precipitation in the autumn. The procedure carried out for Paterno is repeated for Busachi; Figure 6 shows the annual cumulative precipitation trend. Figure 5: Trends in the number of hours (events) with intense precipitation (greater than 3.6 mm/h), on an annual basis and on a seasonal basis (winter and autumn), for the Paterno case study. As in Paterno, there seems to be a reduction in precipitation patterns for Busachi: starting in 2014 a lack of smoothness in the trend of interannual cumulative precipitation is observed. Now, it is useful to look at seasonal trends to see what the contribution of individual seasons might be to the overall annual contribution. Figure 7a,b shows the cumulative seasonal precipitation trends. Figure 7a shows how Busachi has experienced a reduction in winter cumulative precipitation over the past twenty years, while in autumn an increase has been experienced.