Hydroclimatic controls link atmospheric circulation to seasonal landslide timing across the western Mediterranean

Landslide hazard is commonly characterized through event frequency or rainfall thresholds, yet shifts in seasonal timing can also reshape the seasonal hazard window. Here we show that seasonal landslide timing across the western Mediterranean has been regionally reorganized, with large-scale atmospheric circulation influencing this reorganization through precipitation-related hydroclimatic conditions. Using rainfall-triggered landslide records and hydroclimatic data from 1991 to 2020, we identify contrasting regional shifts in landslide timing within the annual cycle. Quantitative causal-effect analyses indicate a seasonal partition in hydroclimatic controls on landslide timing: a one-standard-deviation increase in extreme precipitation frequency and antecedent wetness delays autumn landslide timing by approximately 9 and 5 days, respectively, whereas wetter antecedent conditions advance summer timing by approximately 7 days. Climate projections are used to characterize the future hydroclimatic context of these drivers, suggesting declining antecedent wetness under high-emission scenarios and more regionally variable timing conditions related to extreme precipitation. Hydroclimatic conditions are linked to changes in when landslides occur across the western Mediterranean, delaying autumn landslide timing and advancing summer timing, according to a study using rainfall-triggered landslide records and hydroclimatic data from 1991–2020.