Climate anomalies and geomorphic hazards in high-mountain regions in the Alps: new perspectives from the integrated use of observations and satellite-based products

High-elevation mountainous regions are experiencing an increase in the frequency of mass-wasting processes related to climate-change. Understanding the interplay between the climatic triggers (temperature and precipitation, in particular) and their effects on the dynamics of surface processes is crucial for developing reliable predictive models and for quantifying vulnerability and risk associated with these hazards.

In this work, we exploit a consolidated statistical-based approach in which triggering conditions are identified as climatic anomalies (i.e., non-exceedance probability below/above the 10^th/90^th percentile) in temperature and precipitation values at multiple temporal scales occurred in the lead-up of the events triggering. Specifically, we integrate the traditionally used in-situ information from daily weather stations with: (a) high-resolution (0.1°, 30-min) precipitation estimates from the Integrated Multi-Satellite Retrievals from GPM (IMERG) and (b) daily gridded temperature observations from ENSEMBLES OBServation (E-OBS). We investigate the use of these freely available gridded climatological datasets as an integration/surrogate for in-situ measurements.

Our analysis is based on a database of 358 geomorphic hazards occurred across the Italian Alps in the period 2000-2015, including landslides, rockfalls and debris flows. Preliminary results indicate that IMERG could significantly improve precipitation information by providing estimates directly on the initiation zones, which is particularly relevant in case of hazards triggered by small-scale convective storms. This advantage is evident and in particular for the case of debris flows: IMERG allows to detect precipitation in numerous cases (~60%) for which in-situ data showed no precipitation; in ~19% of these, climatic anomalies (exceedance of the 90^th percentile) are detected.

Further results on the role of sub-daily precipitation processes, particularly relevant for hazards triggered by convective rainfall, such as debris and mud flows, and on the use of temperature data from E-OBS, as being evaluated and will be presented.