The Last 500 Years
North America Drought Variability
E.R. Cook, D.M. Meko, D.W. Stahle, and M.K.Cleaveland, with Gille, E.P., Overpeck, J.T., Karl, T.R., and Guttman, N.B.
Complete Scientific References
This animation displays the spatial patterns of the Palmer Drought Severity Index (PDSI), reconstructed from tree rings, for every year from 1700 to 1978. A network of tree-ring chronologies extending across the U.S. were used to reconstruct summer (June-July-August) drought for each grid point shown in the map (lower left). Each PDSI map was generated from the set of grid point values for that year. From 1895, the maps of reconstructed PDSI are paired with maps from instrumental PDSI records, enabling a comparison between reconstructed and observed PDSI. In general, the PDSI reconstructions mimic the general patterns of drought in the instrumental record, but show less severity. They are conservative estimates of drought, but are still very useful for evaluating the major 20th century droughts in the context of the past 300 years.
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