Teleconnection between the Low Index Phase of Southern Oscillation and Precipitation Patterns over the Southeastern United States

Abstract

The purpose of this analysis is to examine the spatiotemporal extent to which the extreme phase of Southern Oscillation affects precipitation patterns over the southeastern region of the United States. Composite and harmonic analyses using monthly precipitation data were conducted based on the 2-year composite resulting in harmonic dials, which represent the spatial coherence of the candidate regions. For the candidate regions identified in the harmonic dial maps, aggregate composite and index time series of precipitation were analyzed to determine the core regions which represent the temporal consistency in relation to the low index phase of Southern Oscillation (LISO) events. As a result, the precipitation patterns of the core regions, North Region (UR), Middle Region (MR), and South Region (LR), were influenced by the occurrence of the extreme phase of SO events, with SR having the greatest response. During the LISO cycle, the harmonic dial tends to face southeast in UR, northeast in MR, and east in LR. Furthermore, the spatial coherence rates of the three core regions range from 0.94 to 0.99, and the temporal consistency rates are 0.76 to 0.83. In addition, from the cross-correlation and annual cycle analyses, the seasonal and annual effect of LISO forcing on the precipitation variability over the three core regions can be recognizable. In conclusion, Southern Oscillation phenomena have a great influence on the precipitation patterns over the southeastern region of the United States.