Directional Reorganization in Multifractal Parameter Space of Precipitation Under Climate Change: The Catalan Internal Basins

Precipitation in Mediterranean regions is characterized by strong intermittency and complex organization across multiple temporal scales, posing challenges for understanding its future evolution under climate change. This study examines projected changes in the multifractal structure of monthly precipitation at 326 stations within the Catalan Internal Basins, using regional climate simulations under RCP4.5 and RCP8.5 scenarios. Multifractal Detrended Fluctuation Analysis (MFDFA) is applied to historical and future series to quantify changes in the central Hölder exponent (α0), spectral width (W), asymmetry (γ), and a normalized Complexity Index (CI). The results indicate a consistent multifractal reorganization in parameter space dominated by spectral asymmetry. While α0 and W show slight decreases, γ exhibits larger variations approaching one standard deviation, reflecting a redistribution of fluctuations and a shift in the relative contribution of scaling regimes. Principal component analysis reveals that projected changes are mainly aligned with the asymmetry axis, especially inland, while coastal stations display more multidimensional responses involving all parameters. These findings suggest that projected climate-change responses are primarily expressed through structural changes in the multifractal spectrum and also reveal an excess of extreme deviations without clear spatial organization. This highlights the relevance of combining directional and statistical analyses to characterize the multifractal response.