Assessing local changes in the frequency of extreme precipitation events at different durations

This thesis studies the frequency of extreme precipitation events in a localized area in Northeastern Italy, in order to determine whether in such area an increasing trend is evident over 25 years, similar to the global pattern. Given the underlying complexity of the described phenomenon, a linear fitting is considered to be inadequate. There- fore, the study is performed employing Generalized Additive Models, which allow for a smoother fit of the data while maintaining a reasonable level of interpretabil- ity. Such analysis is performed in the framework of Extreme Value Theory, using a Peaks Over Threshold approach. Considering the diverging trend for different rain accumulation durations, two intervals are considered, hourly and daily. While on the hourly scale a positive trend is evident, on the daily scale, the trend is less clear. The presence of different trends at different altitudes is also investigated, showing how, although all altitudes displayed a positive trend, higher altitudes showed a stronger trend, underlining the need for particular attention and adoption of dam- age mitigation measures for such fragile areas.