Northern Annular Mode impact on spring climate in the western United States
Article first published online: 3 SEP 2008
Copyright 2008 by the American Geophysical Union.
Geophysical Research Letters
Volume 35, Issue 17, September 2008
How to Cite
2008), Northern Annular Mode impact on spring climate in the western United States, Geophys. Res. Lett., 35, L17701, doi:10.1029/2008GL034828., and (
- Issue published online: 3 SEP 2008
- Article first published online: 3 SEP 2008
- Manuscript Accepted: 22 JUL 2008
- Manuscript Revised: 26 JUN 2008
- Manuscript Received: 29 MAY 2008
- Northern Annular Mode;
- western United States
 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.