Pacific Ocean SST and Z500 climate variability and western US seasonal streamflow

The current study focuses on evaluating the relationship between the Pacific Ocean climate variability and western US streamflow for six hydrologic regions of the western United States, as defined by United States Geological Survey: Rio Grande, Upper Colorado, Lower Colorado, Great Basin, Pacific Northwest, and California. The singular-valued decomposition (SVD) technique was applied on data for 50 years (1960-2010) of sea-surface temperatures (SST), geopotential height index of 500 mbar (Z(500)), and 90 unimpaired western US streamflows; the results established a spatio-temporal association for each major hydrologic region in the western United States with Pacific Oceanic variability. An approach using a 3- to 9-month lead time was utilized, i.e. the previous year's July to August SST/Z(500), the previous year's October to December SST/Z(500) to predict streamflow for current year spring-summer (April to September), spring (April to June), and summer (July to September) seasons. Significant regions in the Pacific were identified that influence hydrology of the western United States. The traditional El Nino/Southern Oscillation (ENSO) and Pacific Decadal Oscillation regions were identified along with regions over eastern Russia, Canadian British Columbia, and the Hondo' region along the east coast of Japan. Z(500) showed pronounced association with 3-month lead time streamflow, whereas SST had better association with 6-month lead time streamflow. The SVD results showed improvement in correlation values of smaller spatial regions over larger regions, and a lagged response of adjacent hydrologic regions to the same physical indicators. The results obtained in this study could be helpful in improving the current forecasting models for water management.