The drought data are in the form of summer (June-July-August) average Palmer Drought Severity Index. Negative PDSI values indicate dry conditions, while positive values indicate wet conditions. PDSI values generally fall between -6 and +6.
In 1999, a gridded network of PDSI reconstructions for the continental United States (Cook et al. 1999) were generated from a set of 388 tree-ring chronologies. Data are displayed in the form of annual contour maps, and in graphed time series for individual grid points. Maps and data from graphs can be downloaded, as well as the entire set of instrumental and reconstructed data.
In August 2004, the spatial and temporal coverage of the PDSI reconstructions
was expanded (Cook et al. 2004). The
new grid includes 286 points
in a
2.5 degree grid covering most of North America. The PDSI reconstructions
are based on an expanded network of 835
tree-ring chronologies (602 western).
The temporal coverage has been expanded to the maximum permitted by the available
tree ring data, extending back nearly 2000 years
for some locations. The instrumental PDSI series have been extended up
through 2003.
The new reconstructions are currently available from this site in
numerical form and as
time series plots (which can also be accessed along with other NOAA
Paleoclimatology data via an
ArcIMS GIS interface); the mapping display tools are being updated to display
the expanded network.
Additional information on drought can be found in these recent publications. Also see our Paleo Perspective on North American Drought.
These pages were developed jointly by the NOAA Paleoclimatology
Program,
the National Geophysical
Data Center and the National Climatic
Data Center. The 2004 reconstructions were funded by the Earth System History (ESH) of the National Science Foundation in a grant to E.R. Cook.
The PDSI reconstructions can be displayed as either a time series of data values at one location, or as a color map display of PDSI values (1999 version only) for a given year for the continental US.
PDSI Data Links
- Cook et al. 2008 PDSI data set (Version 2a) - Annual Maps Page and Time Series Page. Reconstructions only for now. (calibration and verification data to come soon. Contact Ed Cook for more information.)
- Cook et al. 2004 PDSI time series page and Annual Maps Page (Cook et al. 2004 version, most of North America)
-
Zhang et al. 2004 PDSI time series page (Zhang et al. 2004, Uses Cook '99 grid, USA Only)
-
Cook et al. 1999 PDSI time series page (Cook et al. 1999
version, USA only)
-
Go to annual PDSI maps (1999 version, USA only)
-
NCDC
Drought Pages
- North American Drought Atlas (2004 version) at Lamont-Doherty Earth Observatory Tree Ring Lab. Includes additional PDSI maps and animations.
