noaa-recon-22454 Living Blended Drought Atlas (LBDA) Version 2 - recalibrated reconstruction of United States Summer PMDI over the last 2000 years Gille, E.P.; Wahl, E.R.; Vose, R.S.; Cook, E.R. Living Blended Drought Atlas (LBDA) Version 2 - recalibrated reconstruction of United States Summer PMDI over the last 2000 years 2017-08-03 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/22454 Investigator E.P. Gille Investigator E.R. Wahl Investigator R.S. Vose Investigator E.R. Cook earth science paleoclimate climate reconstructions|tree ring age,null,null,year Common Era,null,climate reconstructions|tree ring,null,null,N,null earth science paleoclimate climate reconstructions|tree ring Palmer Modified Drought Index,null,null,dimensionless,Jun-Aug,climate reconstructions|tree ring,null,null,N,null earth science paleoclimate climate reconstructions|tree ring latitude,null,null,degree north,null,climate reconstructions|tree ring,null,null,N,null earth science paleoclimate climate reconstructions|tree ring longitude,null,null,degree east,null,climate reconstructions|tree ring,null,null,N,null earth science paleoclimate reconstructions geoscientificInformation Palmer Drought Index Reconstruction drought 0 AD 2017 AD 1950 cal yr BP -67 cal yr BP Complete 24 50 -124 -68 Continent North America United States Of America Continental United States>LATITUDE >LONGITUDE None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Cook, E.R., Seager, R., Heim, R.R., Vose, R.S., Herweijer, C., and Woodhouse, C. 2010 Journal of Quaternary Science 25 1 48-61 10.1002/jqs.1303

IPCC Assessment Report 4 model projections suggest that the subtropical dry zones of the world will both dry and expand poleward in the future due to greenhouse warming. The US Southwest is particularly vulnerable in this regard and model projections indicate a progressive drying there out to the end of the 21st century. At the same time, the USA has been in a state of drought over much of the West for about 10 years now. While severe, this turn of the century drought has not yet clearly exceeded the severity of two exceptional droughts in the 20th century. So while the coincidence between the turn of the century drought and projected drying in the Southwest is cause for concern, it is premature to claim that the model projections are correct. At the same time, great new insights into past drought variability over North America have been made through the development of the North American Drought Atlas from tree rings. Analyses of this drought atlas have revealed past megadroughts of unprecedented duration in the West, largely in the Medieval period about 1000 years ago. A vastly improved Living Blended Drought Atlas (LBDA) for North America now under develop- ment reveals these megadroughts in far greater detail. The LBDA indicates the occurrence of the same Medieval megadroughts in the West and similar-scale megadroughts in the agriculturally and commercially important Mississippi Valley. Possible causes of these megadroughts and their implications for the future are discussed. STUDY NOTES: The half degree gridded Jun-Aug PMDI reconstructions from Cook et al. (2010) were recalibrated using the Global Historical Climatology Network (GHCN) 5km grid PMDI data. The 5km data were first upscaled to match the original half-degree grid. The recalibration was performed using a kernel density distribution mapping (KDDM) technique outlined in McGinnis et al. (2015) using an R-package provided by Seth McGinnis. We used a 50-year recalibration period covering 1929-1978 CE. We also adjusted each grid point's mean PMDI value for the recalibration period to be zero to avoid importing wet or dry bias into the recalibration. The recalibrated data set covers the continental United States just as the GHCN instrumental data does. Since instrumental data was used for 1979–2005 CE in the Cook dataset, recalibration applied only to the years 0–1978 CE. The 1979-2017 instrumental years were filled in using data from NCEI's GHCN 5km instrumental PMDI data.

GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/nclimgrid_pmdi-2017.nc netCDF File; GHCN 5km PMDI used for recalibration and instrumental years GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/images/ Data Folder; Collection of Annual U.S. PMDI maps GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_rowyears_2017.txt Text Data File; Data in column format - each row contains one year of data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_template.txt NOAA Template File; Study Description and Metadata Only GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_cols_2017.txt NOAA Template File; Data in column format - each row contains a PMDI data point (large file) GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_kddm_pmdi_2017.nc netCDF File; All PMDI Data in netCDF3 format USA/NOAA DIF Version 9.8.4 2019-05-17 2019-05-17