Drought Evolution Patterns in the U.S.A. During Great Plains-Centered Droughts

This study examines the spatial evolution of drought severity within the contiguous United States during the first six months of average Great Plains-centered drought events. It identifies Great Plains-centered drought events from 1895-1989 based on the drought history of the North Central, South Dakota and Low Rolling Plains, Texas climatic divisions. Time series of warmand cold-season average drought severity based on Great Plains drought for all United States' climatic divisions are calculated and spatially analyzed. Mapped patterns show spatial teleconnections in drought development. Cold-season drought patterns based on the North Central, South Dakota climatic division are clearly in-phase with droughts in the lower Mississippi Valley. Drought patterns based on the Low Rolling Plains, Texas climatic division reveal that droughts are in-phase across the southwestern United States, but are largely out-of-phase with the eastern states. Previous studies on Great Plains drought cover a wide range of topics, including examinations of the synoptic meteorological conditions associated with severe drought periods (Namias 1982; Dey 1982, Chang and Wallace 1987), evaluations of the spatial patterns and temporal persistence of drought conditions (Skaggs 1978; McGregor 1985; Oladipo 1986), searches for periodicities (Oladipo 1987), eigenvector analyses (Klugman 1978), historical and dendroclimatic reconstructions ofGreat Plains drought history (Stockton and Meko 1983; Mock 1991), and examinations of the social aspects of drought (Hecht 1983; Taylor et al. 1987). Other studies focusing on characteristics of drought throughout the United States have helped reinforce the common and substantiated belief that Great Plains' droughts are more tenacious than droughts in other regions of the United States (Walsh et al. 1982; Karl and Koscielny 1982; Diaz 1983; Karl 1983;