Multifractals and the study of extreme precipitation events: A case study from semi-arid and humid regions in Portugal

Precipitation is a highly non-linear hydrologic process that exhibits wide variability over a broad range of time and space scales. This variability involves a large dynamic range, which in certain cases leads to catastrophic events, both related to drought and flood situations. It is thus important to analyze precipitation with methods that have the potential to assess the full range of precipitation fluctuations. Multifractal theory can play an important role in such studies. Moreover, multifractal methods are innovative for the analysis of extremes, offering practical tools for assessing correctly their probability of occurrence. This work presents results of the multifractal analysis of precipitation time series from semi-arid and humid regions in Portugal, concentrating on the statistics of extreme events. The data were recorded daily over a period of more than 50 years.