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Tree-ring carbon isotope data and drought maps
for the U.S. Southwest


Isotope Drought Index and Ancillary Maps
Maps of the Isotope Drought Index have been generated for pentads (1600-1604 through 1995-1999) and for individual years (1985 through 1999). Ancillary maps of Southwestern land-cover and land-use are also available.

Ancillary Maps of Southwestern Land-Cover and Land-Use
We have provided ancillary maps (Appendix D) for contextual assessment of the Isotope (Drought) Index maps. The ancillary maps provide details on the land cover type, individual plant functional type coverage, cropping, as well as topographic elevation, river catchment area and irrigation. The land cover map is taken from the MODIS global land cover mapping of Friedl et al. (2002). Plant functional type, cropping and bare soil mapping were taken from the MODIS Vegetation Continuous Fields data set of Hansen et al. (2003) and historical cropping data set of Ramankutty and Foley (1999) as described in Lawrence and Chase (2006). Irrigation was taken from the global UNFAO AQUASTAT Version 4.0 dataset of Siebert et al. (2006). The digital elevation and river catchment area mapping were both derived from the global USGS GTOPO30 dataset of Siebert et al. (2006).
1. Land cover types
2. Bare soil cover
3. Broadleaf tree cover
4. Needleleaf tree cover
5. C3 grass cover
6. C4 grass cover
7. Shrub cover
8. Crop cover
9. Irrigation cover
10. Elevation
11. Catchment area

Pentad Isotope Drought Index Maps
PDSI Color Scale
Isotope Drought Index Maps Color Scale

Contour Map Filled Contour Map Error Map
1600-041600-041600-04
1605-091605-091605-09
1610-141610-141610-14
1615-191615-191615-19
1620-241620-241620-24
1625-291625-291625-29
1630-341630-341630-34
1635-391635-391635-39
1640-441640-441640-44
1645-491645-491645-49
1650-541650-541650-54
1655-591655-591655-59
1660-641660-641660-64
1665-691665-691665-69
1670-741670-741670-74
1675-791675-791675-79
1680-841680-841680-84
1685-891685-891685-89
1690-941690-941690-94
1695-991695-991695-99
1700-041700-041700-04
1705-091705-091705-09
1710-141710-141710-14
1715-191715-191715-19
1720-241720-241720-24
1725-291725-291725-29
1730-341730-341730-34
1735-391735-391735-39
1740-441740-441740-44
1745-491745-491745-49
1750-541750-541750-54
1755-591755-591755-59
1760-641760-641760-64
1765-691765-691765-69
1770-741770-741770-74
1775-791775-791775-79
1780-841780-841780-84
1785-891785-891785-89
1790-941790-941790-94
1795-991795-991795-99
1800-041800-041800-04
1805-091805-091805-09
1810-141810-141810-14
1815-191815-191815-19
1820-241820-241820-24
1825-291825-291825-29
1830-341830-341830-34
1835-391835-391835-39
1840-441840-441840-44
1845-491845-491845-49
1850-541850-541850-54
1855-591855-591855-59
1860-641860-641860-64
1865-691865-691865-69
1870-741870-741870-74
1875-791875-791875-79
1880-841880-841880-84
1885-891885-891885-89
1890-941890-941890-94
1895-991895-991895-99
1900-041900-041900-04
1905-091905-091905-09
1910-141910-141910-14
1915-191915-191915-19
1920-241920-241920-24
1925-291925-291925-29
1930-341930-341930-34
1935-391935-391935-39
1940-441940-441940-44
1945-491945-491945-49
1950-541950-541950-54
1955-591955-591955-59
1960-641960-641960-64
1965-691965-691965-69
1970-741970-741970-74
1975-791975-791975-79
1980-841980-841980-84
1985-89 Spline*1985-89 Spline*1985-89 Spline*
1985-89 Avg.*1985-89 Avg.*1985-89 Avg.*
1990-94 Spline*1990-94 Spline*1990-94 Spline*
1990-94 Avg.*1990-94 Avg.*1990-94 Avg.*
1995-99 Spline*1995-99 Spline*1995-99 Spline*
1995-99 Avg.*1995-99 Avg.*1995-99 Avg.*

*For the 1985-89, 1990-94 and 1995-99 pentads, two separate calculations have been made. One set is based on a spline fit to the pentad values of the whole sequence, i.e. from the first pentad for the site through 1995-99, where the δ13C values of pentads 1985-89, 1990-94 and 1995-99 are the mean δ13C values of the 5 individual rings in the pentad. The second set is based on calculating the drought indices for the 15 individual years 1985-99 by fitting a straight-line through the δ13C data, and then the drought indices of pentads 1985-89, 1990-94 and 1995-99 are the mean of the 5 annual drought indices so calculated from the straight-line fit.


Individual Year Isotope Drought Index Maps
Contour Map Filled Contour Map Error Map
198519851985
198619861986
198719871987
198819881988
198919891989
199019901990
199119911991
199219921992
199319931993
199419941994
199519951995
199619961996
199719971997
199819981998
199919991999
200020002000
200120012001
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Last Updated Wednesday, 20-Aug-2008 11:24:07 EDT by paleo@noaa.gov
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