Subregionalization of Low-Frequency Summer Drought Variability in the Southeastern United States

Freshwater resources are particularly limited in the Southeastern United States. In recent years, severe summer droughts have placed substantial strain on municipal and industrial water resources, emphasizing the need for further research on the causes of long-term moisture deficits. Previous research has identified a Southeast drought region and specific low-frequency ocean-atmosphere influences on drought. In this article, we identify three distinct subregions of low-frequency summer drought variability in the Southeastern United States using principal components analysis. Multidecadal drought variability is most pronounced in the Southeastern Atlantic Coastal States (SEACS) subregion. The SEACS drought variability is significantly associated with ocean-atmosphere variability in the Atlantic and Pacific basins. The significance of ocean-atmosphere influences on drought in the Southeast is spatially confined within only the SEACS subregion. The Eastern Gulf States (EGS) subregion exhibits a long-term increase in summer moisture that is significantly associated with Northern Hemisphere surface temperature increases during the last century. The peninsular Florida subregion is characterized by high-frequency drought variability that is not associated with any of the climate indexes included in this study.