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Tree-Ring Based Reconstruction of Multi-Year Summer Droughts in Piedmont and Coastal Plain Climate Divisions of the Southeastern U.S., 1690-2006

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Jason T. Ortegren (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Advisor
Paul Knapp

Abstract: The development of summer drought reconstructions for 12 Piedmont and Coastal Plain climate divisions in the southeastern U.S. from existing and original tree-ring chronologies is described. The drought metric reconstructed is the Palmer Meteorological Drought Index (PMDI), a modification of the Palmer Drought Severity Index (PDSI). A composite chronology of average yearly growth index values from individual chronologies covers the common period 1690-1984. The reconstructions have been tested for validity using PMDI data not included in regression modeling. The reconstructions included 6 periods of sustained (> 4 yr) summer drought in the study area during the period 1690-1900. The instrumental record (1900-2006) contains 5 such droughts. Two periods of multi-year summer drought more severe than any in the observed record were found in the reconstructions, the most recent of which ended around 1821. After 1900, prolonged summer droughts in the Piedmont exhibited similar severity to historic droughts, but were more frequent. The data indicate that interactions between the contemporary synoptic features which control drought climatology in the region (e.g., the El-Niño-Southern Oscillation, the Atlantic Multidecadal Oscillation, the north Atlantic subtropical anticyclone, and winter mid-latitude cyclone tracks) discourage the development of multi-decadal droughts of the type that periodically affect the interior American West. Long-term reconstructions suggest "megadroughts" are unlikely in the southeastern U.S. in the absence of significant modification of dominant features of the general atmospheric circulation.

Additional Information

Publication
Dissertation
Language: English
Date: 2008
Keywords
drought, Piedmont, Coastal Plain, climate divisions, southest, United States, tree-ring, Palmer Meteorological Drought Index (PMDI), Palmer Drought Severity Index (PDSI), chronology, 1690-1984, El-Niño-Southern Oscillation, Atlantic Multidecadal Oscillation, north Atlantic subtropical anticyclone, winter mid-latitude cyclone tracks
Subjects
Droughts $z Southern States $x History.
Tree-rings.
Dendrochronology $z Southern States.