Reconstructing landslide probability trends in the Alps: the role of atmospheric circulation patterns

Precipitation-induced landslides are a major hazard worldwide, and their frequency and intensity are expected to rise under climate change, especially in the Alps, which are warming at twice the global average rate. This study reconstructs past landslide susceptibility trends in South Tyrol (Italy) from 1980–2020 using a data-driven model that integrates dynamic precipitation factors—both antecedent and triggering—alongside static terrain attributes. After addressing inventory incompleteness and spatial bias, the model estimates the expected daily landslide susceptibility at 30x30 meters spatial resolution, providing a baseline for climate impact assessments.

To explore atmospheric drivers, landslide susceptibility predictions were associated with the Jenkinson and Collison Weather Types classification scheme. Such synoptic classification was based on daily mean sea-level pressure data from NCAR/NCEP Reanalysis at 2.5º resolution, using a 16-grid-point configuration. Given the broad spatial influence of the weather types, landslide probability predictions were averaged over the entire South Tyrol region, allowing the analysis to focus exclusively on their temporal evolution.

Changes in landslide probability prediction, in relation to the reference period 1980-1995, were analysed seasonally (April to September and October to March). Results for each season were decomposed into frequency effects, capturing how changes in the occurrence of specific weather types affected the overall landslide susceptibility, and impact effects, quantifying how the susceptibility associated with particular weather types has changed over time.

Results show an increase in landslide susceptibility, with a clear seasonal shift toward later peaks in winter. The winter increase is predominantly impact-driven and is stronger in association with the southerly and cyclonic regimes, which carry warm, moist Mediterranean air, while the summer months display smaller increase, mostly associated with frequency changes.

Overall, the findings highlight that evolving atmospheric circulation—particularly enhanced susceptibility under moist advection regimes—rather than uniform shifts in circulation frequency, is intensifying landslide hazard. This underscores the need for adaptation strategies that account for changing hydro-meteorological conditions within circulation patterns, especially during the cold season.