Interconnections between oceanic–atmospheric indices and variability in the U.S. streamflow

Abstract

Summary This study evaluates the relationship between two indicators of climate variability – sea surface temperatures (SST) and 500-mbar geopotential height (Z500) – and seasonal streamflows i.e., spring–summer (March to August), spring (March to May), and summer (June to August) of the continental United States. 240 unimpaired streamflow stations in the continental United States, categorized by hydrologic regions, are analyzed for a 60 year period from 1950 to 2010. Statistical approach comprising of singular value decomposition is used to evaluate the spatio-temporal association between fall (September to November from 1950 to 2009) and winter (December to February from 1950 to 2009) SST and Z500, and the continental U.S. seasonal streamflow. Influences of the interdecadal-warm and cold phases of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) were also evaluated. Regions of highly correlated SST and Z500 were identified that did not have the bias of conservative index regions. Better seasonal variability in streamflow was represented by Z500, compared to SST. Pacific SST had strong correlations with the Midwest, southern South-Atlantic-Gulf, and Pacific Northwest regions, whereas the Atlantic SST had strong correlations with New England, South-Atlantic-Gulf, and Upper and Lower Colorado regions. Stronger correlation of the Pacific and Atlantic Z500 were noticed with the Midwest, New England, Souris-Red-Rainy, Arkansas-White-Red, and Texas-Gulf regions. Interdecadal-temporal evaluation of the phases of the PDO and AMO showed variations in SST regions influencing streamflows and weakening of teleconnections. There were strong correlations of PDO warm phases with most of California, Upper and Lower Colorado, and South-Atlantic-Gulf regions; the PDO cold phases had correlations with Pacific Northwest, eastern Ohio, and South-Atlantic-Gulf regions. The warm phase of AMO showed correlations with Midwest, Souris-Red-Rainy, Upper Mississippi, Arkansas-White-Red, and Texas-Gulf region; the AMO cold phase showed correlations with Upper and Lower Colorado, Midwest, eastern U.S., and South-Atlantic-Gulf. The El Nino Southern Oscillation region 3.4, 3 as well as regions in the central and north tropical Pacific Ocean had strong associations with U.S. streamflow. The hydroclimatic associations identified through the current study may be used to improve streamflow predictability and enhance management of streamflow volumes, several months in advance.