United States Streamflow Probabilities and
Uncertainties based on Anticipated El Niño, Water Year
2003
Michael D.Dettinger
1
Daniel R.Cayan 1
Kelly T.Redmond
2
1 U.S.Geological Survey,Scripps Institution of
Oceanography,La Jolla,CA
2 Western Regional
Climate Center,Desert Research Institute,Reno,NV
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Outlook from article is
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During the course of spring and summer 2002, tropical sea-surface temperatures
in the eastern Pacific Ocean have warmed and the wind and pressure fields have
shifted, so that by August, there was considerable confidence that water year
(October-September) 2003 will be characterized by a weak to mild El Niño
climate.
Streamflow during historical El Niños may have been most notable for the
variability that the warm events impart in many regions of the US. The range
of streamflow conditions during past El Niños have been anomalously large
in absolute terms in the Southwest, upper Midwest, and parts of the Southeast.
The ranges have been large in relative terms in Northwest and Appalachian
rivers.
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Outlook
In the midst of these uncertainties, there are nonetheless
important regional signals. Historically, El Niño years have brought, on
average, increases in mean flows (and flood sizes) in the Southwestern
U.S. and east-central states, and decreases in the Northwest and parts
of the Southeast (excluding Florida). Thus, drought conditions that
currently exist in the Southwest could see some relief but there is
reason for concern in the interior Northwest and in the mid-Atlantic
states.
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