In contrast with the point-by-point (PPR) local regression technique
used previously by Cook, the tree-ring data were calibrated against the
instrumental record of summer drought (June-August Palmer Drought
Severity Index (PDSI)) based on application of the Regularized
Expectation Maximization (RegEM) algorithm to relate large-scale
patterns of variation in proxy and instrumental data over a common
(twentieth century) interval. See complete Data Set Description for more details and to download entire data set.|
| Additionally, a regional analysis was done.
The PDSI field was separated into eight relatively homogenous regions of summer
drought through a cluster analysis.|
|Values for 1700 - 1894 are reconstructed.
Data for 1895 to 1978 are instrumental data from Cook et al 1999.|
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