Evaluating the Relationship between Western U.S. Streamflow and Pacific Ocean Climate Variability

Abstract

The proximity of Pacific Ocean influences the streamflow of the western United States. This study focused on understanding the spatio-temporal relationships between Pacific Ocean and western U.S. streamflow variability by using singular valued decomposition (SVD). A lagged time approach of sea surface temperature (SST) and 500 mbar geopotential height (Z500) over 50 years (1950 to 2010) of unimpaired seasonal streamflow is used for six hydrologic regions of the western United States. Regions of the Pacific SST and Z500 were identified, that showed significant relationships with the western U.S. streamflow. Both combined analysis of western U.S. and individual analysis of each hydrologic region helped in comparing the similarities and differences of the relationships of streamflows with Pacific variability. The temporal expansion series obtained from the first mode of SVD explained majority of the variance. The ENSO and PDO regions, as well as regions over eastern Russia, British Columbia, and east coast of Japan showed significant relationships with streamflow. The Pacific Northwest region showed opposite relationships compared to other hydrologic regions. The correlation values obtained from temporal expansion series were higher for individual hydrologic regions in comparison to the combined western U.S. results. Observed difference in lagged relationship of the individual basins was seen for similar regions of Pacific variability, which can be attributed to regional factors of micro-climate. This study helps to increase our understanding of seasonal relationships of the Pacific with western U.S. streamflows.