Coupled Oceanic-Atmospheric Variability at Different Temporal Scales and U.S. Precipitation Characteristics

A comprehensive examination of the influences of interdecadal, decadal and interannual oceanic-atmospheric oscillations on U.S. precipitation characteristics and extremes is carried out in this study. Four major oscillations affecting the precipitation patterns in the U.S. are evaluated within two phases (cool/negative and warm/positive phases) for each of the oscillations: El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO). Nine extreme precipitation indices, Inter-Event Time Definition (IETD) parameters, dry and wet spell transitions and correlations are analyzed along with parametric statistical hypothesis tests to validate significant changes from one phase to another. The analysis is carried out for the entire continental U.S. at a spatial resolution of 0.125 degree for the period 1950-1999. Analyses confirm spatially non-uniform changes in the influence of the oscillations on precipitation characteristics along with temporal variations over major hydrological basins of the U.S.