Linking atmospheric river hydrological impacts on the U.S. West Coast to Rossby wave breaking

Huancui Hu, Francina Dominguez, Zhuo Wang, David A. Laversa, Gan Zhang, F. Martin Ralph

Research output: Contribution to journalArticlepeer-review


Atmospheric rivers (ARs) have significant hydrometeorological impacts on the U.S. West Coast. This study presents the connection between the characteristics of large-scale Rossby wave breaking (RWB) over the eastern North Pacific and the regional-scale hydrological impacts associated with landfalling ARs on the U.S. West Coast (36°-49°N). ARs associated with RWB account for two-thirds of the landfalling AR events and >70% of total AR-precipitation in the winter season. The two regimes of RWB-anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB)-are associated with different directions of the vertically integrated water vapor transport (IVT). AWB-ARs impinge in a more westerly direction on the coast whereas CWB-ARs impinge in a more southwesterly direction. Most of the landfalling ARs along the northwestern coast of the United States (states of Washington and Oregon) are AWB-ARs. Because of their westerly impinging angles when compared to CWB-ARs, AWB-ARs arrive more orthogonally to the western Cascades and more efficiently transform water vapor into precipitation through orographic lift than CWB-ARs. Consequently, AWB-ARs are associated with the most extreme streamflows in the region. Along the southwest coast of the United States (California), the southwesterly impinging angles of CWB-ARs are more orthogonal to the local topography. Furthermore, the southwest coast CWB-ARs have more intense IVT. Consequently, CWB-ARs are associated with the most intense precipitation. As a result, most of the extreme streamflows in southwest coastal basins are associated with CWB-ARs. In summary, depending on the associated RWB type, ARs impinge on the local topography at a different angle and have a different spatial signature of precipitation and streamflow.

Original languageEnglish (US)
Pages (from-to)3381-3399
Number of pages19
JournalJournal of Climate
Issue number9
StatePublished - May 1 2017


  • Hydrometeorology
  • Mass fluxes/transport
  • Orographic effects
  • Water vapor
  • Wave breaking

ASJC Scopus subject areas

  • Atmospheric Science


Dive into the research topics of 'Linking atmospheric river hydrological impacts on the U.S. West Coast to Rossby wave breaking'. Together they form a unique fingerprint.

Cite this