How climate change may reorganize rainfall patterns in Catalunya

What is it about?

Rainfall is not distributed evenly over time. In Mediterranean regions such as Catalonia, long dry periods can occur alongside short periods of very intense rainfall. Climate change may alter not only the amount and frequency of rainfall, but also the way rainfall variability is organized over different time scales. In this study, we analysed monthly precipitation projections from 326 meteorological stations in the Catalan Internal Basins. We used multifractal analysis to describe features of rainfall variability that are not captured by conventional measures alone. We then combined these indicators with multivariate analysis to investigate how rainfall characteristics may change under two climate scenarios (RCP4.5 and RCP8.5), and whether the changes differ between coastal and inland areas. We found that the projected changes are not simply an overall increase or decrease in rainfall complexity. Instead, the multifractal characteristics tend to move in a preferential direction, with spectral asymmetry emerging as the most sensitive parameter. The spatial pattern also suggests a coastal–inland gradient, indicating that climate change may reorganize rainfall variability differently across the region.

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Photo by Wolfgang Weiser on Unsplash

Photo by Wolfgang Weiser on Unsplash

Why is it important?

Understanding these changes matters because rainfall patterns strongly influence water availability, drought, runoff and flood risk. Conventional climate indicators usually describe changes in rainfall amount, frequency or intensity, but they may not capture changes in the underlying structure of rainfall variability. Our results suggest that climate change can modify this structure even when the overall change in conventional rainfall indicators is not straightforward. The fact that the projected changes follow a preferential direction in multifractal parameter space provides an additional way of detecting and characterizing climate-change signals. The coastal–inland differences identified in the study are also relevant for regional climate and water-management planning, particularly in a Mediterranean region where water scarcity and intense rainfall events coexist.