USGS Washington Water Science Center
|U.S. Department of the Interior
U.S. Geological Survey
Release: December 11, 2002
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[Note: The report can be viewed on the Web at http://pubs.water.usgs.gov/wri024176/ .]
Long periods of wet and dry weather in the Pacific Northwest are linked to weather conditions in the North and South Pacific Oceans that result in changes in local streamflow, according to the results of a study published today by the U.S. Geological Survey.
The USGS examined sea-surface temperatures and air circulation on a regional-to-global scale, looking for linkages to streamflow, rainfall, and temperature in the Pacific Northwest. From the available data, scientists identified three separate climate periods--pre-1947, 1947-76, and post-1976.
"Of the three periods, pre-1947 and post-1976 are drier and warmer," said John J. Vaccaro, USGS hydrologist and author of the report. "The shift in 1947 to a wetter, colder period is linked to the global climate, and the shift in 1977 back to a drier, warmer period is linked to conditions in the North Pacific."
Vaccaro noted that recent work by other scientists indicates that the drier, warmer period that started after 1976 may have ended as of 1996.
Understanding the causes for these two major shifts in the climate of the Pacific Northwest is essential for best management of water resources, including reservoirs, flood control, and drought.
The report, "Interdecadal Changes in the Hydrometeorological Regime of the Pacific Northwest and in the Regional-to-Hemispheric Climate Regimes, and Their Linkages," by J.J. Vaccaro, is published as U.S. Geological Survey Water-Resources Investigations Report 02-4190. The report is available on-line at http://pubs.water.usgs.gov/wri024176/. Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone 303-202-4200.
The USGS, a bureau within the Department of the Interior, serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.
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