Snowpack Contributions and Temperature Characterization of Landfalling Atmospheric Rivers in the Western Cordillera of the United States

This study utilized long-term daily precipitation and snow-water equivalent (SWE) data derived from the Natural Resources Conservation Service’s Snow Telemetry Network. All existing SNOTEL sites in the Olympic, Coast and Cascade ranges in Washington (n = 66) and Oregon (n = 52) and in the California Sierra Nevada (n = 28) with data from water year 1984 to water year 2016 were included in this analysis. The Topography Weather data from Oyler et al. (2015) were used in this analysis due to systemic artifacts in the raw SNOTEL data. Average daily temperatures were computed as the mean of daily minimum and maximum temperatures. Atmospheric river data were obtained from Jonathan Rutz’s “AR catalogs” and identified by a combination of feature length and integrated water vapor flux transport thresholds (IVT250) as described in Rutz et al. (2014). The Modern-Era Retrospective Analysis for Research and Applications (MERRA) data set was used for both its spatial resolution (0.5˚) and temporal coverage (from 1980–2017). Data spanning 38–49˚N and 116.25–125˚W were extracted for this study. Keywords: Atmospheric river; Hydroclimatology; Snowpack; West Coast; Extreme snowfall;