Abstract:
[1] A study of the influence of interdecadal, decadal, and interannual oceanic atmospheric
influences on streamflow in the United States is presented. Unimpaired
streamflow was identified for 639 stations in the United States for the period 1951–2002.
The phases (cold/negative or warm/positive) of Pacific Ocean (El Nino–Southern
Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and Atlantic Ocean (Atlantic
Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO)) oceanic atmospheric
influences were identified for the year prior to the streamflow year (i.e., long
lead time). Statistical significance testing of streamflow, based on the interdecadal,
decadal, and interannual oceanic-atmospheric phase (warm/positive or cold/negative), was
performed by applying the nonparametric rank-sum test. The results show that in addition
to the well-established ENSO signal the PDO, AMO, and NAO influence streamflow
variability in the United States. The warm phase of the PDO is associated with increased
streamflow in the central and southwest United States, while the warm phase of the
AMO is associated with reduced streamflow in these regions. The positive phase of the
NAO and the cold phase of the AMO are associated with increased streamflow in the
central United States. Additionally, the coupled effects of the oceanic-atmospheric
influences were evaluated on the basis of the long-term phase (cold/negative or warm/
positive) of the interdecadal (PDO and AMO) and decadal (NAO) influences and ENSO.
Streamflow regions in the United States were identified that respond to these climatic
couplings. The results show that the AMO may influence La Nina impacts in the
Southeast, while the NAO may influence La Nina impacts in the Midwest. By utilizing the
streamflow water year and the long lead time for the oceanic-atmospheric variables, useful
information can be provided to streamflow forecasters and water managers.
