Feb 4, 2015

Changes in Winter Atmospheric Rivers along the North American West Coast in CMIP5 Climate Models

by
Michael D. Warner, Clifford F. Mass, and Eric P. Salathé
,
Journal of Hydrometeorology
  • States that global climate models have sufficient resolution to simulate synoptic features associated with atmospheric river (AR) events, such as high values of vertically integrated water vapor transport (IVT) approaching the coast
  • Uses 10 simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to identify changes in ARs impacting the west coast of North America between historical (1970–99) and end-of-century (2070–99) runs, using representative concentration pathway (RCP) 8.5
  • Identifies the most extreme ARs in both time periods by the 99th percentile of IVT days along a north–south transect offshore of the coast
  • Finds that integrated water vapor (IWV) and IVT are predicted to increase, while lower-tropospheric winds change little
  • Finds that winter mean precipitation along the west coast increases by 11%–18% [from 4% to 6% (°C)−1], while precipitation on extreme IVT days increases by 15%–39% [from 5% to 19% (°C)−1]
  • Finds that the frequency of IVT days above the historical 99th percentile threshold increases as much as 290% by the end of this century