Jun 22, 2007

Meteorological Characteristics and Overland Precipitation Impacts of Atmospheric Rivers Affecting the West Coast of North America Based on Eight Years of SSM/I Satellite Observations

by
Paul J. Neiman, F. Martin Ralph, Gary A. Wick, Jessica D. Lundquist, Michael D. Dettinger
,
American Meteorological Society
  • Investigates landfalling atmospheric rivers (ARs) along adjacent north- and south-coast regions of western North America
  • Detects ARs just offshore over the eastern Pacific from 1997 to 2005 using Special Sensor Microwave Imager (SSM/I) satellite observations of long, narrow plumes of enhanced integrated water vapor (IWV)
  • Finds that the north coast experienced 301 AR days, while the south coast had only 115
  • Finds that most ARs occurred during the warm season in the north and cool season in the south, despite the fact that the cool season is climatologically wettest for both regions
  • Finds that ARs generally increase snow water equivalent (SWE) in autumn/winter and decrease SWE in spring
  • Finds that, on average, wintertime snow water equivalent exhibits normal gains during north-coast AR storms and above-normal gains during the south-coast AR storms
  • Finds that wintertime ARs with the largest SSM/I IWV are tied to more intense storms with stronger flows and vapor fluxes, and more precipitation
  • Finds that the north-coast sites are mostly lower in altitude, where warmer-than-normal conditions more frequently yield rain and that flooding is more likely to occur during those events when heavy rain from a warm AR storm falls on a preexisting snowpack