Seasonal controls and memory of soil moisture variability across Italy: a process-oriented perspective relevant to landslide preconditioning

Soil moisture plays a central role in slope hydrology by integrating atmospheric forcing and subsurface processes, thereby shaping antecedent wetness conditions relevant to landslide preconditioning. A key property governing this role is soil moisture memory, defined as the persistence of moisture anomalies following external perturbations. Despite its importance, the seasonal organization of soil moisture memory and its physical controls remain insufficiently constrained at regional scales.

This study focuses on understanding how soil moisture variability across Italy is organized by the interplay between external hydro-meteorological forcing and internal system persistence across seasons. Specifically, using high-resolution gridded reanalysis-based data within a causal discovery framework, the analysis examines the seasonal dominance of different drivers and the spatial and temporal variability of soil moisture persistence, with emphasis on large-scale background hydrological states.

The results indicate pronounced spatial and seasonal heterogeneity. Soil moisture variability is primarily governed by atmospheric water inputs over large portions of the domain, while cryospheric and energy-related processes become relevant under specific climatic and seasonal conditions. Crucially, soil moisture persistence exhibits systematic seasonal contrasts and is not uniformly associated with the apparent strength of external forcing. The joint behavior of forcing strength and memory instead organizes soil moisture dynamics into distinct seasonal regimes, reflecting different modes of system response shaped by land–atmosphere coupling and soil water loss processes. These findings support a physically consistent interpretation of antecedent wetness conditions relevant to landslide preconditioning.