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Abstract. Rainfall-Induced Landslide Early Warning Systems (RILEWS) are critical tools for reducing and mitigating economic and social damages related to landslides. Despite this critical need, the Southern Andes does not yet possess an operational-scale system to support decision-makers. We propose RILEWS using a logistic regression system in the Southern Andes. The models were forced by corrected simulations of precipitation and geomorphological features. We evaluated the precipitation using the Weather and Research Forecast (WRF) model on an hourly scale. The precipitation was corrected using bias correction approaches with daily data from 12 meteorological stations. Four logistic and probabilistic models were then calibrated using Logit and Probit distributions. The predictor variables used were combinations of the slope, corrected daily precipitation and data preceding the events (7 and 30 days previous) for 57 Rainfall-Induced Landslides (RIL); validation was by ROC analysis. Our results showed that WRF does not represent the spatial variability of the precipitation. This situation was resolved by bias correcting. Specifically, the PP_M4a method with Bernoulli distribution for the occurrence and Gamma for the intensity produced lower MAE and RMSE values and higher correlation values. Finally, our RILEWS had a high predicting capacity with an AUC of 0.80 using daily precipitation data and slope. We conclude that our methodology is suitable at an operational level in the Southern Andes. Our contribution could become a useful tool in the mitigation of impacts related to climate change.

In a large part of South America, slow landslides are triggered by extreme hydrometeorological conditions leading to, for instance, Rainfall-Induced Landslides – RILs. These RILs are common in urban areas and have a negative impact on the population and infrastructure development. Despite their importance, these events are little understood. We aimed at understanding the spatial distribution of RILs in the urban zone of Temuco, Chile (38.8°S, 72.6°W). The area has the typical hydrometeorological conditions of southern Chile. We conducted our assessment with a temporal analysis of shallow deformations, obtained by synthetic aperture radar interferometry (Sentinel 1 A/B). These shallow deformation rates were compared with satellite precipitation data (CHIRPS product) and electrical resistivity tomography (ERT). We identified active RIL-prone zones with deformation rates greater than 60 mm during the period 2014 to 2017, supporting theories of hydrometeorological control. Slow movements were observed in volcanic soils, suggesting the influence of their geotechnical characteristics. Our results can be extrapolated to the southern Andes (35°S-43°S), where a large number of volcanic-sedimentary units are susceptible to RILs. Finally, integration of our multidisciplinary approach will facilitate understanding of the local RIL dynamics, allowing a better risk management to decision-makers in South American and other developing countries.

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<p>Mesoscale Convective Systems (MCSs) are associated with an important fraction of total precipitation in the vicinity of the Tropical Andes, and are related to high impact weather events and extreme rainfall.  Important ingredients include input of moisture and synoptic conditions particular of each location, depending on the regional scale circulation and the local topography.  Convection-Permitting (CP) simulations can help to better describe events with MCSs, including details of surface processes, low-level moisture transport and mountain-related circulations. Here we present a description of two MCSs in the vicinity of the Tropical Andes based on gridded observation-based data (ERA5 and GPM), in situ measurements and CP simulations with the Weather Research and Forecasting (WRF) model.  One of the events took place near the Andes-Amazon transition region (Mocoa-Colombia), with, reportedly, more than 100mm of precipitation accumulated in 3 hours in one location, accompanied with strong low-level transport of moisture by the (nocturnal) Orinoco Low-Level Jet (OLLJ) and strong mid-tropospheric easterly winds towards the Andes, favorable for orographic enhancenment of precipitation.  The other event took place over the low-lands of the Magdalena-Cauca basin (Cordoba-Colombia), with an approximate size of 71304 km<sup>2 </sup>, according to its cloud top temperature pattern.  In this region a sea-breeze provides moisture from oceanic origin, and the nearby Andes might help to enhance low-level convergence via orographic blocking and other mountain-related effects.  Based on kilometer-scale CP simulations we describe details of the initiation and life cycle of these two MCSs as simulated by WRF, including a description of the low-level input of moisture provided by the sea-breeze and the nocturnal jet during the initiation and mature stages, the corresponding mesoscale circulations in the vicinity of the Andes, and the intensity of the simulated precipitation.  Preliminary 3-km simulations of the Mocoa event show the low-level flow blocking by the Andes, the enhanced orographic precipitation, and an underestimation of the maximum intensity of rainfall. This study might help on understanding the skill and limitations of CP simulations for representing weather systems associated to extreme rainfall in the Tropical Andes. </p>