Northern annular mode impact on spring climate in the western United States

Stephanie A. McAfee, Joellen L. Russell

Research output: Contribution to journalArticlepeer-review

68 Scopus citations


Shifts in stormtrack position associated with the Northern Annular Mode (NAM) are linked to temperature changes and reduced spring precipitation in the western United States. During the transition to spring following a high-index winter, weakening of the stormtrack over the northeastern Pacific Ocean and western United States is shown to lead to warmer and drier conditions west of the Rocky Mountains and increased precipitation just east of the Rocky Mountains, consistent with observations of early spring onset in the western United States. Given projected increases in the average annular mode index and associated poleward shifts in the stormtrack, this analysis provides additional evidence that much of the western United States will experience more severe drought conditions over the next several decades, irrespective of changes in temperature, because of an earlier shift to warm-season circulation patterns.

Original languageEnglish (US)
Article numberL17701
JournalGeophysical Research Letters
Issue number17
StatePublished - Sep 16 2008

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


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