Atmospheric River Families and their Relationship to Landslides in Washington State

Precipitation has long been identified as a driver for landslides, and atmospheric rivers are often associated with precipitation events that trigger landslides. This study aims to connect synoptic regimes to geomorphic responses in Washington State. Specifically, we aim to determine how atmospheric river families (two or more AR events occurring within up to 120 hours) affect occurrence of landslides; this relates to how quickly soil moisture and other properties recover following atmospheric river events. We examine several mapped shallow landslide events reported by the Washington Geological Survey and compare their occurrence to sequences of atmospheric rivers, precipitation, soil moisture, and other properties. Our study includes analysis of an atmospheric river with integrated vapor transport peaking at 1463 kg m^-1 s^-1 on December 3, 2007, leading to over 1,940 landslides and killing one person in Western Washington. Further understanding of the connection between synoptic regimes during atmospheric river families in combination with ground-based observations preceding past landslide events could provide insight into improved lead time in forecasting landslide activity.