Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States

doi:10.1073/pnas.0306738101

Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States

^*U.S. Geological Survey, Denver Federal Center, MS 412, Denver, CO 80225; ^‡Midwestern Regional Climate Center, Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820; and ^§U.S. Geological Survey, Desert Laboratory, 1675 West Anklam Road, Tucson, AZ 85745

Edited by Inez Y. Fung, University of California, Berkeley, CA, and approved January 12, 2004 (received for review October 17, 2003)

Abstract

More than half (52%) of the spatial and temporal variance in multidecadal drought frequency over the conterminous United States is attributable to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). An additional 22% of the variance in drought frequency is related to a complex spatial pattern of positive and negative trends in drought occurrence possibly related to increasing Northern Hemisphere temperatures or some other unidirectional climate trend. Recent droughts with broad impacts over the conterminous U.S. (1996, 1999–2002) were associated with North Atlantic warming (positive AMO) and northeastern and tropical Pacific cooling (negative PDO). Much of the long-term predictability of drought frequency may reside in the multidecadal behavior of the North Atlantic Ocean. Should the current positive AMO (warm North Atlantic) conditions persist into the upcoming decade, we suggest two possible drought scenarios that resemble the continental-scale patterns of the 1930s (positive PDO) and 1950s (negative PDO) drought.

Footnotes

↵ † To whom correspondence should be addressed. E-mail: gmccabe{at}usgs.gov.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: SST, sea surface temperature; PDO, Pacific Decadal Oscillation; AMO, Atlantic Multidecadal Oscillation; NH, Northern Hemisphere.