Climate and streamflow patterns in Australia associated with El Niño/Southern Oscillation

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The dominant spatial and temporal modes of streamflow variability in the Western U.S. during ENSO events are investigated using Principal Component Analysis (PCA), Bootstrap resampling, and Jackknife analysis. The spatial variability is investigated by extracting the six dominant modes of rotated PCA on 93 streamflow stations in the Western U.S. conditioned upon El Nino years. The six dominant modes represent regions, or clusters, that tend to co-vary together during ENSO events. The ENSO response in streamflow is further evaluated by forming an aggregate ENSO composite for each region. The Statistical significant threshold levels (e.g. 90%) are established with a Bootstrap resampling procedure. In three of the six regions, representing the Pacific Northwest and Rocky Mountain states, the streamflow anomalies are consistently (for at least 3 months) above the 90% confidence level. Within the regions identified using PCA, the temporal variability of the western U.S. streamflow during ENSO is evaluated with a Jackknife analysis. That is, the influence of individual ENSO events on the overall ENSO composite is evaluated. This procedure identifies ENSO events which have a significantly different response, as seen in streamflow, than "normal" ENSO events. The analysis breaks the 12 El Nino events that occurred from 1932 to 1988 into three subsets. The first subset is considered to be the "normal" ENSO response in streamflow. The other two subsets are years which the ENSO response is anomalously strong or the ENSO response is opposite that of the normal ENSO response in streamflow. The results of this study provide insight to the different "flavors" of western U.S. streamflow variability during ENSO events.


El Nino-Southern Oscillation (ENSO); Streamflow; Precipitation; Runoff; Water supply


Environmental Sciences | Fresh Water Studies | Meteorology


Presented at the American Geophysical Union, 1995 Fall Meeting, San Francisco, California, December 11-15.


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