The role of atmospheric rivers in rainfall-induced landslides: A study from the Elqui valley

Abstract

The purpose of the present study is to explore the synoptic-scale atmospheric circulation and water vapor transport that contribute to triggering landslides in the mid-Elqui basin (30 degrees S, 70.5 degrees W) since the early 20th century. A total of 12 storms during the modern period (1957-2017) were identified from various sources and analyzed using ERA5 Reanalysis data. An additional set of eight storms was included and characterized using 20th Century Reanalysis data. The results reveal that high-amplitude, deep troughs extending into the subtropics off the west coast of South America are ubiquitous in these storms. Maximum integrated water vapor transport from the northwest (NW) or west-northwest (WNW) was observed on the coast (25-30 degrees S), with values sometimes exceeding 300 kg s-1 m-1, often reaching more than five standard deviations above the mean. Atmospheric rivers near the study region were found to be involved in all 12 modern landslide-producing storms. Moreover, most storms occur during the warm phase of the El Nin & SIM;o-Southern Oscillation (ENSO) and/or phases 7-8-1 of the Madden-Julian Oscillation (MJO). Backward-trajectory analyses indicate that in all but one of the modern storms, water vapor transport originated in the Central Tropical Pacific, where ocean warming characterizes the convective phases of ENSO and/or MJO.