On Exploring Trends in Atmospheric River Induced Precipitation Extremes on the U.S. West Coast

Historical extreme heavy rainfalls in many parts of the world have been linked to naturally occurring Atmospheric River (AR) phenomena. When interacting with topography that involves large mountain ranges such as the Cascade–Sierra ranges in Western US, ARs produce intense precipitation and large storms. In this study, we explore the link between heavy precipitations and landfall ARs over the period 1988-2017 on US West Coast. We detect atmospheric river conditions in terms of Integrated Vapor Transport (IVT) exceeding an established threshold using ERA-Interim data. Time series of daily precipitation observations are obtained from 560 Global Historical Climate Network (GHCN) stations with record of 20 years and longer. Selected climate change detection indices and Mann-Kendall significant test are used to explore spatio-temporal trends in precipitation. Generalized extreme value (GEV) distribution is used to model various return levels of daily annual maximum precipitation related to AR. The results will have implications in short-term stormwater management, flood risk analysis, and long-term climate forecast.